RECLAIM SYSTEM TABLE

Use the RECLAIM SYSTEM TABLE statement to make orphan system table rows as deleted and/or recover the RAM they are using.

Usage

RECLAIM SYSTEM TABLE ROWS | RAM | ROWS AND RAM

Notes

Kognitio uses a “lazy delete” method to delete system table rows which are obsolete. For example, when a table is dropped, its row in IPE_ALLTABLE is deleted, but the dependent rows in IPE_ALLBASE, IPE_ALLCOLUMN, and other system tables are not. These rows are deleted on the next CREATE [SYSTEM] IMAGE operation.

If CREATE [SYSTEM] IMAGE is not run regularly, it is possible that these orphan system table rows will use significant RAM and also slow down queries on the system tables. To address that the RECLAIM SYSTEM TABLE command has been provided.

To recover the RAM used by deleted system table rows, the command acquired a global lock, which means no other sessions can be connected – a script can be used to abort other sessions before running the command. Note that all variants of the command complete very quickly, so the interruption to normal usage is very short.

The ROWS option specifies that orphan rows should be deleted.

The RAM option specifies that the RAM used by deleted system table rows should be recovered.

Combining the two options with ROWS AND RAM results in orphan rows being deleted, then RAM occupied by deleted system table rows is recovered.