# Preset Options > Complete dossiers for 24 core PostgreSQL settings in Preset Options. --- Dossier URLs remain flat; this category exists only to organize browsing and the sidebar. --- Section pages: - [block_size](/parameters/block-size/): block_size — Shows the size of a disk block. Observed in PG9.0–19 Beta 3; its last measured boot default is 8192 in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [data_checksums](/parameters/data-checksums/): data_checksums — Shows whether data checksums are turned on for this cluster. Observed in PG9.3–19 Beta 3; its last measured boot default is off in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [data_directory_mode](/parameters/data-directory-mode/): data_directory_mode shows the mode of the data directory. It is read-only metadata in PG11–18, not a runtime tuning control. - [debug_assertions](/parameters/debug-assertions/): debug_assertions — Shows whether the running server has assertion checks enabled. Observed in PG9.0–19 Beta 3; its last measured boot default is off in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [debug_exec_backend](/parameters/debug-exec-backend/): debug_exec_backend — Shows whether the running server is built with EXEC_BACKEND enabled. Observed in PG19 Beta 3; its last measured boot default is off in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [effective_wal_level](/parameters/effective-wal-level/): effective_wal_level — Shows effective WAL level. Observed in PG19 Beta 3; its last measured boot default is replica in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [huge_pages_status](/parameters/huge-pages-status/): huge_pages_status indicates the status of huge pages. It is read-only metadata in PG17–18, not a runtime tuning control. - [in_hot_standby](/parameters/in-hot-standby/): in_hot_standby shows whether hot standby is currently active. It is read-only metadata in PG14–18, not a runtime tuning control. - [integer_datetimes](/parameters/integer-datetimes/): integer_datetimes — Shows whether datetimes are integer based. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [lc_collate](/parameters/lc-collate/): lc_collate — Shows the collation order locale. Observed in PG9.0–15; its last measured boot default is C in PG15, with internal context. It was removed in PG16. - [lc_ctype](/parameters/lc-ctype/): lc_ctype — Shows the character classification and case conversion locale. Observed in PG9.0–15; its last measured boot default is C in PG15, with internal context. It was removed in PG16. - [max_function_args](/parameters/max-function-args/): max_function_args — Shows the maximum number of function arguments. Observed in PG9.0–19 Beta 3; its last measured boot default is 100 in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [max_identifier_length](/parameters/max-identifier-length/): max_identifier_length — Shows the maximum identifier length. Observed in PG9.0–19 Beta 3; its last measured boot default is 63 in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [max_index_keys](/parameters/max-index-keys/): max_index_keys — Shows the maximum number of index keys. Observed in PG9.0–19 Beta 3; its last measured boot default is 32 in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [num_os_semaphores](/parameters/num-os-semaphores/): num_os_semaphores — Shows the number of semaphores required for the server. Observed in PG18–19 Beta 3; its last measured boot default is 0 in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [segment_size](/parameters/segment-size/): segment_size — Shows the number of pages per disk file. Observed in PG9.0–19 Beta 3; its last measured boot default is 1 GiB (131072 × 8kB) in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [server_encoding](/parameters/server-encoding/): server_encoding — Shows the server (database) character set encoding. Observed in PG9.0–19 Beta 3; its last measured boot default is SQL_ASCII in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [server_version](/parameters/server-version/): server_version — Shows the server version. Observed in PG9.0–19 Beta 3; its last measured boot default is 19beta3 (Debian 19~beta3-1.pgdg13+1) in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [server_version_num](/parameters/server-version-num/): server_version_num — Shows the server version as an integer. Observed in PG9.0–19 Beta 3; its last measured boot default is 190000 in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [shared_memory_size](/parameters/shared-memory-size/): shared_memory_size shows the size of the server's main shared memory area (rounded up to the nearest MB). It is read-only metadata in PG15–18, not a runtime tuning control. - [shared_memory_size_in_huge_pages](/parameters/shared-memory-size-in-huge-pages/): shared_memory_size_in_huge_pages shows the number of huge pages needed for the main shared memory area. It is read-only metadata in PG15–18, not a runtime tuning control. - [ssl_library](/parameters/ssl-library/): ssl_library shows the name of the SSL library. It is read-only metadata in PG12–18, not a runtime tuning control. - [wal_block_size](/parameters/wal-block-size/): wal_block_size — Shows the block size in the write ahead log. Observed in PG9.0–19 Beta 3; its last measured boot default is 8192 in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA. - [wal_segment_size](/parameters/wal-segment-size/): wal_segment_size — Shows the size of write ahead log segments. Observed in PG9.0–19 Beta 3; its last measured boot default is 16 MiB in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.