> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/15/internals/54.-system-views/overview.md). # 54.1. Overview [Table 54.1](https://www.postgresql.org/docs/current/views-overview.html#VIEW-TABLE) lists the system views. More detailed documentation of each catalog follows below. Except where noted, all the views described here are read-only. #### **Table 54.1. System Views** | View Name | Purpose | | ---------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------- | | [`pg_available_extensions`](https://www.postgresql.org/docs/current/view-pg-available-extensions.html) | available extensions | | [`pg_available_extension_versions`](https://www.postgresql.org/docs/current/view-pg-available-extension-versions.html) | available versions of extensions | | [`pg_backend_memory_contexts`](https://www.postgresql.org/docs/current/view-pg-backend-memory-contexts.html) | backend memory contexts | | [`pg_config`](https://www.postgresql.org/docs/current/view-pg-config.html) | compile-time configuration parameters | | [`pg_cursors`](https://www.postgresql.org/docs/current/view-pg-cursors.html) | open cursors | | [`pg_file_settings`](https://www.postgresql.org/docs/current/view-pg-file-settings.html) | summary of configuration file contents | | [`pg_group`](https://www.postgresql.org/docs/current/view-pg-group.html) | groups of database users | | [`pg_hba_file_rules`](https://www.postgresql.org/docs/current/view-pg-hba-file-rules.html) | summary of client authentication configuration file contents | | [`pg_ident_file_mappings`](https://www.postgresql.org/docs/current/view-pg-ident-file-mappings.html) | summary of client user name mapping configuration file contents | | [`pg_indexes`](https://www.postgresql.org/docs/current/view-pg-indexes.html) | indexes | | [`pg_locks`](https://www.postgresql.org/docs/current/view-pg-locks.html) | locks currently held or awaited | | [`pg_matviews`](https://www.postgresql.org/docs/current/view-pg-matviews.html) | materialized views | | [`pg_policies`](https://www.postgresql.org/docs/current/view-pg-policies.html) | policies | | [`pg_prepared_statements`](https://www.postgresql.org/docs/current/view-pg-prepared-statements.html) | prepared statements | | [`pg_prepared_xacts`](https://www.postgresql.org/docs/current/view-pg-prepared-xacts.html) | prepared transactions | | [`pg_publication_tables`](https://www.postgresql.org/docs/current/view-pg-publication-tables.html) | publications and information of their associated tables | | [`pg_replication_origin_status`](https://www.postgresql.org/docs/current/view-pg-replication-origin-status.html) | information about replication origins, including replication progress | | [`pg_replication_slots`](https://www.postgresql.org/docs/current/view-pg-replication-slots.html) | replication slot information | | [`pg_roles`](https://www.postgresql.org/docs/current/view-pg-roles.html) | database roles | | [`pg_rules`](https://www.postgresql.org/docs/current/view-pg-rules.html) | rules | | [`pg_seclabels`](https://www.postgresql.org/docs/current/view-pg-seclabels.html) | security labels | | [`pg_sequences`](https://www.postgresql.org/docs/current/view-pg-sequences.html) | sequences | | [`pg_settings`](https://www.postgresql.org/docs/current/view-pg-settings.html) | parameter settings | | [`pg_shadow`](https://www.postgresql.org/docs/current/view-pg-shadow.html) | database users | | [`pg_shmem_allocations`](https://www.postgresql.org/docs/current/view-pg-shmem-allocations.html) | shared memory allocations | | [`pg_stats`](https://www.postgresql.org/docs/current/view-pg-stats.html) | planner statistics | | [`pg_stats_ext`](https://www.postgresql.org/docs/current/view-pg-stats-ext.html) | extended planner statistics | | [`pg_stats_ext_exprs`](https://www.postgresql.org/docs/current/view-pg-stats-ext-exprs.html) | extended planner statistics for expressions | | [`pg_tables`](https://www.postgresql.org/docs/current/view-pg-tables.html) | tables | | [`pg_timezone_abbrevs`](https://www.postgresql.org/docs/current/view-pg-timezone-abbrevs.html) | time zone abbreviations | | [`pg_timezone_names`](https://www.postgresql.org/docs/current/view-pg-timezone-names.html) | time zone names | | [`pg_user`](https://www.postgresql.org/docs/current/view-pg-user.html) | database users | | [`pg_user_mappings`](https://www.postgresql.org/docs/current/view-pg-user-mappings.html) | user mappings | | [`pg_views`](https://www.postgresql.org/docs/current/view-pg-views.html) | views | --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.postgresql.tw/15/internals/54.-system-views/overview.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.