IBM PureData System for Analytics, Version 7.1

Reorganize the table data

After you specify the organizing key or keys for a table, records are inserted into the CBT as they would be for a non-CBT table. When you run the GROOM TABLE command, IBM® Netezza® reorganizes the records that are based on the specified keys.

The GROOM TABLE command performs two operations that are important to the user tables on your system:

It organizes the records for a table so that your related records are relocated to the same extents.
It removes the deleted and outdated records in user tables to reclaim disk space on your system.

The GROOM TABLE command processes and reorganizes the table records in each data slice in a series of steps. Users can do tasks such as SELECT, UPDATE, DELETE, and INSERT operations while the online data grooming is taking place. The SELECT operations run in parallel with the groom operations; the INSERT, UPDATE, and DELETE operations run serially between the groom steps. For CBTs, the groom steps are slightly longer than for non-CBT tables, so INSERT, UPDATE, and DELETE operations might pend for a longer time until the current step completes.

Note: When you specify organizing keys for an existing table to make it a CBT, the new organization can affect the compression size of the table. The new organization can create sequences of records that improve the overall compression benefit, or it can create sequences that do not compress as well. Following a groom operation, your table size can change somewhat from its size compared to the previous organization.