System Catalogs for Performance View Snapshot

After enable_wdr_snapshot is set to on, the background snapshot thread creates and maintains a system catalog named in the format of SNAP_View name to record the snapshot result of each performance view. The following system catalogs are accessible only to users with system administrator rights:

• SNAP_PGXC_OS_RUN_INFO
• SNAP_PGXC_WAIT_EVENTS
• SNAP_PGXC_INSTR_UNIQUE_SQL
• SNAP_PGXC_STAT_BAD_BLOCK
• SNAP_PGXC_STAT_BGWRITER
• SNAP_PGXC_STAT_REPLICATION
• SNAP_PGXC_REPLICATION_SLOTS
• SNAP_PGXC_SETTINGS
• SNAP_PGXC_INSTANCE_TIME
• SNAP_GLOBAL_WORKLOAD_TRANSACTION
• SNAP_PGXC_WORKLOAD_SQL_COUNT
• SNAP_PGXC_STAT_DATABASE
• SNAP_GLOBAL_STAT_DATABASE
• SNAP_PGXC_REDO_STAT
• SNAP_GLOBAL_REDO_STAT
• SNAP_PGXC_REL_IOSTAT
• SNAP_GLOBAL_REL_IOSTAT
• SNAP_PGXC_TOTAL_MEMORY_DETAIL
• SNAP_PGXC_NODE_STAT_RESET_TIME
• SNAP_PGXC_SQL_COUNT
• SNAP_GLOBAL_TABLE_STAT
• SNAP_GLOBAL_TABLE_CHANGE_STAT
• SNAP_GLOBAL_COLUMN_TABLE_IO_STAT
• SNAP_GLOBAL_ROW_TABLE_IO_STAT

Except the new snapshot_id column (of the bigint type), the definitions of the other columns in these system catalogs are the same as those of the corresponding views, and the distribution key of each system catalog is snapshot_id.

For example, SNAP_PGXC_OS_RUN_INFO is used to record snapshots of the PGXC_OS_RUN_INFO view. The snapshot_id column is new, and other columns are the same as those of the PGXC_OS_RUN_INFO view.

• The schema of all above system catalogs is dbms_om.
• Do not modify or delete these catalogs externally. Otherwise, functions related to view snapshots may not work properly.