> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-mintlify-fbfa8bee.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

> نظرة عامة على جداول النظام وسبب أهميتها.

# جداول النظام

{/*AUTOGENERATED_START*/}

| الصفحة                                                                                                 | الوصف                                                                                                                                                                                                                       |
| ------------------------------------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [system.constraints](/ar/reference/system-tables/constraints)                                          | System table containing information about existing constraints in all tables.                                                                                                                                               |
| [System Tables Overview](/ar/reference/system-tables/overview)                                         | Overview of what system tables are and why they are useful.                                                                                                                                                                 |
| [INFORMATION\_SCHEMA](/ar/reference/system-tables/information_schema)                                  | System database providing an almost standardized DBMS-agnostic view on metadata of database objects.                                                                                                                        |
| [system.aggregate\_function\_combinators](/ar/reference/system-tables/aggregate_function_combinators)  | Contains a list of all available aggregate function combinators, which could be applied to aggregate functions and change the way they work.                                                                                |
| [system.aggregated\_zookeeper\_log](/ar/reference/system-tables/aggregated_zookeeper_log)              | System table containing aggregated statistics of ZooKeeper operations grouped by session, path, operation type, component, and subrequest flag.                                                                             |
| [system.asynchronous\_insert\_log](/ar/reference/system-tables/asynchronous_insert_log)                | System table containing information about async inserts. Each entry represents an insert query buffered into an async insert query.                                                                                         |
| [system.asynchronous\_loader](/ar/reference/system-tables/asynchronous_loader)                         | System table containing information about and status of recent asynchronous jobs (e.g. for tables which are loading). The table contains a row for every job.                                                               |
| [system.asynchronous\_metric\_log](/ar/reference/system-tables/asynchronous_metric_log)                | System table containing historical values for `system.asynchronous_metrics`, which are saved once per time interval (one second by default)                                                                                 |
| [system.asynchronous\_inserts](/ar/reference/system-tables/asynchronous_inserts)                       | System table containing information about pending asynchronous inserts in queue.                                                                                                                                            |
| [system.asynchronous\_metrics](/ar/reference/system-tables/asynchronous_metrics)                       | System table containing metrics that are calculated periodically in the background. For example, the amount of RAM in use.                                                                                                  |
| [system.azure\_queue\_settings](/ar/reference/system-tables/azure_queue_settings)                      | System table containing information about settings of AzureQueue tables. Available from server version `24.10`.                                                                                                             |
| [system.azure\_queue\_metadata\_cache](/ar/reference/system-tables/azure_queue_metadata_cache)         | Contains in-memory state of AzureQueue metadata and currently processed rows per file.                                                                                                                                      |
| [system.azure\_queue\_log](/ar/reference/system-tables/azure_queue_log)                                | Contains log entries with information about files processed by the AzureQueue engine.                                                                                                                                       |
| It is safe to truncate or drop this table at any time.                                                 |                                                                                                                                                                                                                             |
| [system.background\_schedule\_pool\_log](/ar/reference/system-tables/background_schedule_pool_log)     | System table containing history of background schedule pool task executions.                                                                                                                                                |
| [system.background\_schedule\_pool](/ar/reference/system-tables/background_schedule_pool)              | System table containing information about tasks in background schedule pools.                                                                                                                                               |
| [system.backup\_log](/ar/reference/system-tables/backup_log)                                           | System table containing logging entries with information about `BACKUP` and `RESTORE` operations.                                                                                                                           |
| [system.backups](/ar/reference/system-tables/backups)                                                  | System table containing logging entries with information about `BACKUP` and `RESTORE` operations.                                                                                                                           |
| [system.blob\_storage\_log](/ar/reference/system-tables/blob_storage_log)                              | System table containing logging entries with information about various blob storage operations such as uploads and deletes.                                                                                                 |
| [system.build\_options](/ar/reference/system-tables/build_options)                                     | System table containing information about ClickHouse server's build options.                                                                                                                                                |
| [system.certificates](/ar/reference/system-tables/certificates)                                        | Contains information about available certificates and their sources.                                                                                                                                                        |
| [system.clusters](/ar/reference/system-tables/clusters)                                                | System table containing information about clusters available in the config file and the servers defined in them.                                                                                                            |
| [system.codecs](/ar/reference/system-tables/codecs)                                                    | System table containing information about codecs in queue.                                                                                                                                                                  |
| [system.collations](/ar/reference/system-tables/collations)                                            | Contains a list of all available collations for alphabetical comparison of strings.                                                                                                                                         |
| [system.columns](/ar/reference/system-tables/columns)                                                  | System table containing information about columns in all tables                                                                                                                                                             |
| [system.completions](/ar/reference/system-tables/completions)                                          | Contains a list of completion tokens.                                                                                                                                                                                       |
| [system.contributors](/ar/reference/system-tables/contributors)                                        | System table containing information about contributors.                                                                                                                                                                     |
| [system.crash\_log](/ar/reference/system-tables/crash_log)                                             | System table containing information about stack traces for fatal errors.                                                                                                                                                    |
| [system.current\_roles](/ar/reference/system-tables/current_roles)                                     | System table containing active roles for the current user.                                                                                                                                                                  |
| [system.dashboards](/ar/reference/system-tables/dashboards)                                            | Contains queries used by `/dashboard` page accessible though the HTTP interface. useful for monitoring and troubleshooting.                                                                                                 |
| [system.data\_skipping\_indices](/ar/reference/system-tables/data_skipping_indices)                    | System table containing information about existing data skipping indices in all the tables.                                                                                                                                 |
| [system.data\_skipping\_index\_types](/ar/reference/system-tables/data_skipping_index_types)           | System table containing a list of data skipping index types supported by the server along with their embedded documentation.                                                                                                |
| [system.data\_type\_families](/ar/reference/system-tables/data_type_families)                          | System table containing information about supported data types                                                                                                                                                              |
| [system.database\_engines](/ar/reference/system-tables/database_engines)                               | System table containing a list of database engines supported by the server.                                                                                                                                                 |
| [system.database\_replicas](/ar/reference/system-tables/database_replicas)                             | System table containing information about and status of replicated database.                                                                                                                                                |
| [system.databases](/ar/reference/system-tables/databases)                                              | System table containing information about the databases that are available to the current user.                                                                                                                             |
| [system.dead\_letter\_queue](/ar/reference/system-tables/dead_letter_queue)                            | System table containing information about messages received via a streaming engine and parsed with errors.                                                                                                                  |
| [system.delta\_lake\_metadata\_log](/ar/reference/system-tables/delta_metadata_log)                    | System table containing information about metadata files read from Delta Lake tables. Each entry represents a root metadata JSON file.                                                                                      |
| [system.detached\_parts](/ar/reference/system-tables/detached_parts)                                   | System table containing information about detached parts of MergeTree tables                                                                                                                                                |
| [system.detached\_tables](/ar/reference/system-tables/detached_tables)                                 | System table containing information about each detached table.                                                                                                                                                              |
| [system.dictionaries](/ar/reference/system-tables/dictionaries)                                        | System table containing information about dictionaries                                                                                                                                                                      |
| [system.dictionary\_sources](/ar/reference/system-tables/dictionary_sources)                           | System table containing a list of dictionary sources supported by the server along with their embedded documentation.                                                                                                       |
| [system.dictionary\_layouts](/ar/reference/system-tables/dictionary_layouts)                           | System table containing a list of dictionary layouts supported by the server along with their embedded documentation.                                                                                                       |
| [system.dimensional\_metrics](/ar/reference/system-tables/dimensional_metrics)                         | This table contains dimensional metrics that can be calculated instantly and exported in the Prometheus format. It is always up to date.                                                                                    |
| [system.disk\_types](/ar/reference/system-tables/disk_types)                                           | System table containing a list of disk types supported by the server along with their embedded documentation.                                                                                                               |
| [system.disks](/ar/reference/system-tables/disks)                                                      | System table containing information about disks defined in the server configuration                                                                                                                                         |
| [system.distributed\_ddl\_queue](/ar/reference/system-tables/distributed_ddl_queue)                    | System table containing information about distributed ddl queries (queries using the ON CLUSTER clause) that were executed on a cluster.                                                                                    |
| [system.distribution\_queue](/ar/reference/system-tables/distribution_queue)                           | System table containing information about local files that are in the queue to be sent to the shards.                                                                                                                       |
| [system.dns\_cache](/ar/reference/system-tables/dns_cache)                                             | System table containing information about cached DNS records.                                                                                                                                                               |
| [system.documentation](/ar/reference/system-tables/documentation)                                      | System table that collects the embedded documentation of the uniform components of the system (functions, table engines, data types, and so on) into a single table, with the reference documentation rendered as Markdown. |
| [system.dropped\_tables](/ar/reference/system-tables/dropped_tables)                                   | System table containing information about tables that drop table has been executed on but for which data cleanup has not yet been performed                                                                                 |
| [system.dropped\_tables\_parts](/ar/reference/system-tables/dropped_tables_parts)                      | System table containing information about parts of MergeTree dropped tables from `system.dropped_tables`                                                                                                                    |
| [system.enabled\_roles](/ar/reference/system-tables/enabled_roles)                                     | System table containing all active roles at the moment, including the current role of the current user and the granted roles for the current role                                                                           |
| [system.error\_log](/ar/reference/system-tables/error_log)                                             | System table containing the history of error values from table `system.errors`, periodically flushed to disk.                                                                                                               |
| [system.errors](/ar/reference/system-tables/errors)                                                    | System table containing error codes with the number of times they have been triggered.                                                                                                                                      |
| [system.events](/ar/reference/system-tables/events)                                                    | System table containing information about the number of events that have occurred in the system.                                                                                                                            |
| [system.fail\_points](/ar/reference/system-tables/fail_points)                                         | Contains a list of all available failpoints with their type and current status.                                                                                                                                             |
| [system.filesystem\_cache\_settings](/ar/reference/system-tables/filesystem_cache_settings)            | Contains information about all filesystem cache settings                                                                                                                                                                    |
| [system.filesystem\_read\_prefetches\_log](/ar/reference/system-tables/filesystem_read_prefetches_log) | Contains a history of all prefetches done during reading from MergeTree tables backed by a remote filesystem.                                                                                                               |
| It is safe to truncate or drop this table at any time.                                                 |                                                                                                                                                                                                                             |
| [system.filesystem\_cache\_log](/ar/reference/system-tables/filesystem_cache_log)                      | Contains a history of all events occurred with filesystem cache for objects on a remote filesystem.                                                                                                                         |
| It is safe to truncate or drop this table at any time.                                                 |                                                                                                                                                                                                                             |
| [system.filesystem\_cache](/ar/reference/system-tables/filesystem_cache)                               | Contains information about all entries inside filesystem cache for remote objects.                                                                                                                                          |
| [system.formats](/ar/reference/system-tables/formats)                                                  | Contains a list of all the formats along with flags whether a format is suitable for input/output or whether it supports parallelization.                                                                                   |
| [system.functions](/ar/reference/system-tables/functions)                                              | System table containing information about normal and aggregate functions.                                                                                                                                                   |
| [system.grants](/ar/reference/system-tables/grants)                                                    | System table showing which privileges are granted to ClickHouse user accounts.                                                                                                                                              |
| [system.graphite\_retentions](/ar/reference/system-tables/graphite_retentions)                         | System table containing information about parameters `graphite_rollup` which are used in tables with `GraphiteMergeTree` type engines.                                                                                      |
| [system.histogram\_metrics](/ar/reference/system-tables/histogram_metrics)                             | This table contains histogram metrics that can be calculated instantly and exported in the Prometheus format. It is always up to date.                                                                                      |
| [system.iceberg\_history](/ar/reference/system-tables/iceberg_history)                                 | System iceberg snapshot history                                                                                                                                                                                             |
| [system.iceberg\_files](/ar/reference/system-tables/iceberg_files)                                     | System table containing per-file metadata of Iceberg tables                                                                                                                                                                 |
| [system.iceberg\_metadata\_log](/ar/reference/system-tables/iceberg_metadata_log)                      | System table containing information about metadata files read from Iceberg tables. Each entry represents either a root metadata file, metadata extracted from an Avro file, or an entry of some Avro file.                  |
| [system.instrumentation](/ar/reference/system-tables/instrumentation)                                  | System table containing the instrumentation points                                                                                                                                                                          |
| [system.jemalloc\_stats](/ar/reference/system-tables/jemalloc_stats)                                   | Returns jemalloc statistics in a single row with a single column. Equivalent to SYSTEM JEMALLOC STATS command.                                                                                                              |
| [system.jemalloc\_bins](/ar/reference/system-tables/jemalloc_bins)                                     | System table containing information about memory allocations done via jemalloc allocator in different size classes (bins) aggregated from all arenas.                                                                       |
| [system.jemalloc\_profile\_text](/ar/reference/system-tables/jemalloc_profile_text)                    | Displays the symbolized jemalloc heap profile. Run 'SYSTEM JEMALLOC FLUSH PROFILE' to generate a profile first.                                                                                                             |
| [system.kafka\_consumers](/ar/reference/system-tables/kafka_consumers)                                 | System table containing information about Kafka consumers.                                                                                                                                                                  |
| [system.keeper\_cluster](/ar/reference/system-tables/keeper_cluster)                                   | System table which exists only when this node runs an in-process ClickHouse Keeper. Contains one row per Raft cluster member as seen by this Keeper.                                                                        |
| [system.keeper\_snapshots](/ar/reference/system-tables/keeper_snapshots)                               | System table which exists only when this node runs an in-process ClickHouse Keeper. Contains one row per on-disk Raft snapshot tracked by the Keeper state machine.                                                         |
| [system.keeper\_changelogs](/ar/reference/system-tables/keeper_changelogs)                             | System table which exists only when this node runs an in-process ClickHouse Keeper. Contains one row per on-disk Raft changelog file tracked by the Keeper log store.                                                       |
| [system.keywords](/ar/reference/system-tables/keywords)                                                | Contains a list of all keywords used in ClickHouse parser.                                                                                                                                                                  |
| [system.licenses](/ar/reference/system-tables/licenses)                                                | System table containing licenses of third-party libraries that are located in the contrib directory of ClickHouse sources.                                                                                                  |
| [system.macros](/ar/reference/system-tables/macros)                                                    | Contains a list of all macros defined in server configuration.                                                                                                                                                              |
| [system.masking\_policies](/ar/reference/system-tables/masking_policies)                               | System table containing information about all masking policies in the system.                                                                                                                                               |
| [system.merge\_tree\_settings](/ar/reference/system-tables/merge_tree_settings)                        | System table containing information about settings for MergeTree tables.                                                                                                                                                    |
| [system.merges](/ar/reference/system-tables/merges)                                                    | System table containing information about merges and part mutations currently in process for tables in the MergeTree family.                                                                                                |
| [system.metric\_log](/ar/reference/system-tables/metric_log)                                           | System table containing history of metrics values from tables `system.metrics` and `system.events`, periodically flushed to disk.                                                                                           |
| [system.metrics](/ar/reference/system-tables/metrics)                                                  | System table containing metrics which can be calculated instantly, or have a current value.                                                                                                                                 |
| [system.models](/ar/reference/system-tables/models)                                                    | Contains a list of CatBoost models loaded into a LibraryBridge's memory along with time when it was loaded.                                                                                                                 |
| [system.moves](/ar/reference/system-tables/moves)                                                      | System table containing information about in-progress data part moves of MergeTree tables. Each data part movement is represented by a single row.                                                                          |
| [system.mutations](/ar/reference/system-tables/mutations)                                              | System table containing information about mutations of MergeTree tables and their progress. Each mutation command is represented by a single row.                                                                           |
| [system.named\_collections](/ar/reference/system-tables/named_collections)                             | يحتوي على قائمة بجميع المجموعات المسماة التي أُنشئت عبر استعلام SQL أو جرى تحليلها من ملف الإعدادات.                                                                                                                        |
| [system.numbers\_mt](/ar/reference/system-tables/numbers_mt)                                           | جدول نظام مشابه لـ `system.numbers`، لكن عمليات القراءة تُنفَّذ بالتوازي ويمكن إرجاع الأرقام بأي ترتيب.                                                                                                                     |
| [system.numbers](/ar/reference/system-tables/numbers)                                                  | جدول نظام يحتوي على عمود UInt64 واحد باسم `number`، ويتضمن تقريبًا جميع الأعداد الطبيعية بدءًا من الصفر.                                                                                                                    |
| [system.one](/ar/reference/system-tables/one)                                                          | جدول نظام يحتوي على صف واحد وعمود UInt8 واحد باسم `dummy` يحمل القيمة 0. وهو مشابه للجدول `DUAL` الموجود في أنظمة إدارة قواعد البيانات الأخرى.                                                                              |
| [system.opentelemetry\_span\_log](/ar/reference/system-tables/opentelemetry_span_log)                  | جدول نظام يحتوي على معلومات عن مقاطع التتبع للاستعلامات المنفَّذة.                                                                                                                                                          |
| [system.part\_moves\_between\_shards](/ar/reference/system-tables/part_moves_between_shards)           | يحتوي على معلومات عن الأجزاء التي تكون حاليًا قيد النقل بين الـ shards ومدى تقدمها.                                                                                                                                         |
| [system.part\_log](/ar/reference/system-tables/part_log)                                               | جدول نظام يحتوي على معلومات عن الأحداث التي طرأت على أجزاء البيانات في جداول عائلة MergeTree، مثل إضافة البيانات أو دمجها.                                                                                                  |
| [system.parts](/ar/reference/system-tables/parts)                                                      | جدول نظام يحتوي على معلومات عن أجزاء MergeTree.                                                                                                                                                                             |
| [system.parts\_columns](/ar/reference/system-tables/parts_columns)                                     | جدول نظام يحتوي على معلومات عن الأجزاء والأعمدة في جداول MergeTree.                                                                                                                                                         |
| [system.predicate\_statistics\_log](/ar/reference/system-tables/predicate_statistics_log)              | جدول نظام يحتوي على إحصاءات مُعيَّنة للمرشحات وانتقائية الفهارس، جُمعت من مسارات قراءة `MergeTree` أثناء تنفيذ الاستعلام.                                                                                                   |
| [system.primes](/ar/reference/system-tables/primes)                                                    | جدول نظام يحتوي على عمود UInt64 واحد باسم `prime`، ويتضمن الأعداد الأولية بترتيب تصاعدي بدءًا من 2.                                                                                                                         |
| [system.privileges](/ar/reference/system-tables/privileges)                                            | يحتوي على قائمة بجميع الامتيازات المتاحة التي يمكن منحها لمستخدم أو دور.                                                                                                                                                    |
| [system.processes](/ar/reference/system-tables/processes)                                              | جدول نظام يُستخدم لتنفيذ الاستعلام `SHOW PROCESSLIST`.                                                                                                                                                                      |
| [system.processors\_profile\_log](/ar/reference/system-tables/processors_profile_log)                  | جدول نظام يحتوي على معلومات توصيف على مستوى المعالجات (يمكن العثور عليها في `EXPLAIN PIPELINE`).                                                                                                                            |
| [system.projection\_parts\_columns](/ar/reference/system-tables/projection_parts_columns)              | جدول نظام يحتوي على معلومات عن الأعمدة في أجزاء الإسقاط للجداول التابعة لعائلة MergeTree.                                                                                                                                   |
| [system.projection\_parts](/ar/reference/system-tables/projection_parts)                               | جدول نظام يحتوي على معلومات عن أجزاء الإسقاط للجداول التابعة لعائلة MergeTree.                                                                                                                                              |
| [system.projections](/ar/reference/system-tables/projections)                                          | جدول نظام يحتوي على معلومات عن الإسقاطات الموجودة في جميع الجداول.                                                                                                                                                          |
| [system.query\_views\_log](/ar/reference/system-tables/query_views_log)                                | جدول نظام يحتوي على معلومات عن الـ views التابعة التي تُنفَّذ عند تشغيل استعلام، مثل نوع الـ view أو وقت التنفيذ.                                                                                                           |
| [system.query\_condition\_cache](/ar/reference/system-tables/query_condition_cache)                    | جدول نظام يعرض محتوى ذاكرة التخزين المؤقت لشروط الاستعلام.                                                                                                                                                                  |
| [system.query\_thread\_log](/ar/reference/system-tables/query_thread_log)                              | جدول نظام يحتوي على معلومات عن الخيوط التي تنفّذ الاستعلامات، مثل اسم الخيط ووقت بدئه ومدة معالجة الاستعلام.                                                                                                                |
| [system.query\_metric\_log](/ar/reference/system-tables/query_metric_log)                              | جدول نظام يحتوي على سجل لقيم الذاكرة والمقاييس من الجدول `system.events` للاستعلامات الفردية، ويُفرَّغ دوريًا إلى القرص.                                                                                                    |
| [system.query\_log](/ar/reference/system-tables/query_log)                                             | جدول نظام يحتوي على معلومات عن الاستعلامات المنفَّذة، مثل وقت البدء ومدة المعالجة ورسائل الخطأ.                                                                                                                             |
| [system.query\_cache](/ar/reference/system-tables/query_cache)                                         | جدول نظام يعرض محتوى ذاكرة التخزين المؤقت للاستعلامات.                                                                                                                                                                      |
| [system.quota\_usage](/ar/reference/system-tables/quota_usage)                                         | جدول نظام يحتوي على معلومات عن استخدام الحصص من قِبل المستخدم الحالي، مثل مقدار الحصة المستخدمة ومقدار المتبقي منها.                                                                                                        |
| [system.quota\_limits](/ar/reference/system-tables/quota_limits)                                       | جدول نظام يحتوي على معلومات عن القيم القصوى لجميع الفترات الخاصة بجميع الحصص. ويمكن أن تقابل الحصة الواحدة أي عدد من الصفوف أو حتى صفر صفوف.                                                                                |
| [system.quotas\_usage](/ar/reference/system-tables/quotas_usage)                                       | جدول نظام يحتوي على معلومات عن استخدام الحصص من قِبل جميع المستخدمين.                                                                                                                                                       |
| [system.quotas](/ar/reference/system-tables/quotas)                                                    | جدول نظام يحتوي على معلومات عن الحصص.                                                                                                                                                                                       |
| [system.remote\_data\_paths](/ar/reference/system-tables/remote_data_paths)                            | جدول نظام يحتوي على معلومات عن ملفات البيانات المخزنة على أقراص بعيدة مثل S3 أو Azure Blob Storage.                                                                                                                         |
| [system.replicas](/ar/reference/system-tables/replicas)                                                | جدول نظام يحتوي على معلومات عن الجداول المتماثلة الموجودة على الخادم المحلي وحالتها. وهو مفيد لأغراض المراقبة.                                                                                                              |
| [system.replicated\_merge\_tree\_settings](/ar/reference/system-tables/replicated_merge_tree_settings) | يحتوي على قائمة بجميع الإعدادات الخاصة بمحرك ReplicatedMergeTree، وقيمها الحالية والافتراضية، إلى جانب أوصافها. يمكنك تغيير أيٍّ منها في قسم SETTINGS ضمن استعلام CREATE.                                                   |
| [system.replicated\_fetches](/ar/reference/system-tables/replicated_fetches)                           | System table containing information about currently running background fetches.                                                                                                                                             |
| [system.replication\_queue](/ar/reference/system-tables/replication_queue)                             | System table containing information about tasks from replication queues stored in ClickHouse Keeper, or ZooKeeper, for tables in the `ReplicatedMergeTree` family.                                                          |
| [system.resources](/ar/reference/system-tables/resources)                                              | System table containing information about resources residing on the local server with one row for every resource.                                                                                                           |
| [system.rocksdb](/ar/reference/system-tables/rocksdb)                                                  | Contains a list of metrics exposed from embedded RocksDB.                                                                                                                                                                   |
| [system.role\_grants](/ar/reference/system-tables/role_grants)                                         | System table containing the role grants for users and roles.                                                                                                                                                                |
| [system.roles](/ar/reference/system-tables/roles)                                                      | System table containing information about configured roles.                                                                                                                                                                 |
| [system.row\_policies](/ar/reference/system-tables/row_policies)                                       | System table containing filters for one particular table, as well as a list of roles and/or users which should use this row policy.                                                                                         |
| [system.s3\_queue\_settings](/ar/reference/system-tables/s3_queue_settings)                            | System table containing information about the settings of S3Queue tables. Available from server version `24.10`.                                                                                                            |
| [system.s3queue\_metadata\_cache](/ar/reference/system-tables/s3queue_metadata_cache)                  | Contains in-memory state of S3Queue metadata and currently processed rows per file.                                                                                                                                         |
| [system.s3queue\_log](/ar/reference/system-tables/s3queue_log)                                         | Contains log entries with information about files processed by the S3Queue engine.                                                                                                                                          |
| It is safe to truncate or drop this table at any time.                                                 |                                                                                                                                                                                                                             |
| [system.scheduler](/ar/reference/system-tables/scheduler)                                              | System table containing information about and status of scheduling nodes residing on the local server.                                                                                                                      |
| [system.schema\_inference\_cache](/ar/reference/system-tables/schema_inference_cache)                  | System table containing information about all cached file schemas.                                                                                                                                                          |
| [system.server\_settings](/ar/reference/system-tables/server_settings)                                 | System table containing formation about global settings for the server, which are specified in `config.xml`.                                                                                                                |
| [system.session\_log](/ar/reference/system-tables/session_log)                                         | System table containing information about all successful and failed login and logout events.                                                                                                                                |
| [system.settings](/ar/reference/system-tables/settings)                                                | System table containing information about session settings for current user.                                                                                                                                                |
| [system.settings\_profile\_elements](/ar/reference/system-tables/settings_profile_elements)            | System table which describes the content of the settings profile: constraints, roles and users that the setting applies to, parent settings profiles.                                                                       |
| [system.settings\_changes](/ar/reference/system-tables/settings_changes)                               | System table containing information about setting changes in previous ClickHouse versions.                                                                                                                                  |
| [system.settings\_profiles](/ar/reference/system-tables/settings_profiles)                             | System table which contains properties of configured setting profiles.                                                                                                                                                      |
| [system.stack\_trace](/ar/reference/system-tables/stack_trace)                                         | System table which contains stack traces of all server threads. Allows developers to introspect the server state.                                                                                                           |
| [system.storage\_policies](/ar/reference/system-tables/storage_policies)                               | System table containing information about storage policies and volumes which are defined in server configuration.                                                                                                           |
| [system.symbols](/ar/reference/system-tables/symbols)                                                  | System table useful for C++ experts and ClickHouse engineers containing information for introspection of the `clickhouse` binary.                                                                                           |
| [system.table\_engines](/ar/reference/system-tables/table_engines)                                     | System table containing descriptions of table engines supported by the server and the features they support.                                                                                                                |
| [system.table\_functions](/ar/reference/system-tables/table_functions)                                 | Contains a list of all available table functions with their descriptions.                                                                                                                                                   |
| [system.tables](/ar/reference/system-tables/tables)                                                    | System table containing metadata of each table that the server knows about.                                                                                                                                                 |
| [system.text\_log](/ar/reference/system-tables/text_log)                                               | System table containing logging entries.                                                                                                                                                                                    |
| [system.time\_zones](/ar/reference/system-tables/time_zones)                                           | System table containing a list of time zones that are supported by the ClickHouse server.                                                                                                                                   |
| [system.tokenizers](/ar/reference/system-tables/tokenizers)                                            | System table which shows all available tokenizers.                                                                                                                                                                          |
| [system.trace\_log](/ar/reference/system-tables/trace_log)                                             | System table containing stack traces collected by the sampling query profiler.                                                                                                                                              |
| [system.transactions](/ar/reference/system-tables/transactions)                                        | Contains a list of transactions and their state.                                                                                                                                                                            |
| [system.transactions\_info\_log](/ar/reference/system-tables/transactions_info_log)                    | Contains information about all transactions executed on a current server.                                                                                                                                                   |
| It is safe to truncate or drop this table at any time.                                                 |                                                                                                                                                                                                                             |
| [system.unicode](/ar/reference/system-tables/unicode)                                                  | System table containing a list of Unicode characters and their properties.                                                                                                                                                  |
| [system.user\_processes](/ar/reference/system-tables/user_processes)                                   | System table containing information useful for an overview of memory usage and ProfileEvents of users.                                                                                                                      |
| [system.user\_directories](/ar/reference/system-tables/user_directories)                               | Contains the information about configured user directories - directories on the file system from which ClickHouse server is allowed to read user provided data.                                                             |
| [system.user\_defined\_functions](/ar/reference/system-tables/user_defined_functions)                  | System table containing loading status and configuration metadata for User-Defined Functions (UDFs).                                                                                                                        |
| [system.users](/ar/reference/system-tables/users)                                                      | System table containing a list of user accounts configured on the server.                                                                                                                                                   |
| [system.view\_refreshes](/ar/reference/system-tables/view_refreshes)                                   | System table containing information about Refreshable Materialized Views.                                                                                                                                                   |
| [system.warnings](/ar/reference/system-tables/system_warnings)                                         | This table contains warning messages about clickhouse server.                                                                                                                                                               |
| [system.warnings](/ar/reference/system-tables/warnings)                                                | Contains warnings about server configuration to be displayed by clickhouse-client right after it connects to the server.                                                                                                    |
| [system.workloads](/ar/reference/system-tables/workloads)                                              | System table containing information for workloads residing on the local server.                                                                                                                                             |
| [system.zeros](/ar/reference/system-tables/zeros)                                                      | Produces unlimited number of non-materialized zeros.                                                                                                                                                                        |
| [system.zeros\_mt](/ar/reference/system-tables/zeros_mt)                                               | Multithreaded version of system.zeros.                                                                                                                                                                                      |
| [system.zookeeper\_watches](/ar/reference/system-tables/zookeeper_watches)                             | System table showing currently active ZooKeeper watches registered by this ClickHouse server.                                                                                                                               |
| [system.zookeeper\_info](/ar/reference/system-tables/zookeeper_info)                                   | System table which outputs introspection of all available keeper nodes.                                                                                                                                                     |
| [system.zookeeper\_log](/ar/reference/system-tables/zookeeper_log)                                     | System table containing information about the parameters of the request to the ZooKeeper server and the response from it.                                                                                                   |
| [system.zookeeper\_connection](/ar/reference/system-tables/zookeeper_connection)                       | System table which exists only if ZooKeeper is configured. Shows current connections to ZooKeeper (including auxiliary ZooKeepers).                                                                                         |
| [system.zookeeper\_connection\_log](/ar/reference/system-tables/zookeeper_connection_log)              | Shows the history of ZooKeeper connections (including auxiliary ZooKeepers).                                                                                                                                                |
| [system.zookeeper](/ar/reference/system-tables/zookeeper)                                              | System table which exists only if ClickHouse Keeper or ZooKeeper are configured. It exposes data from the Keeper cluster defined in the config.                                                                             |
