DWS runs SQL statements to perform different system operations, such as setting variables, displaying the execution plan, and collecting garbage data.
For details about how to set various parameters for a session or transaction, see SET.
For details about how to display the execution plan that DWS makes for SQL statements, see EXPLAIN.
By default, WALs periodically specify checkpoints in a transaction log. CHECKPOINT forces an immediate checkpoint when the related command is issued, without waiting for a regular checkpoint scheduled by the system. For details, see CHECKPOINT.
For details about how to collect garbage data and analyze a database as required, For details, see VACUUM.
For details about how to collect statistics on tables in databases, For details, see ANALYZE.
For details about how to set the constraint check mode for the current transaction, For details, see SET CONSTRAINTS.