Home
AdministeringIn addition to administering the database server, you can tune performance, replicate data, and archive data.
System administrationThese topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL OneDB™ database servers.
Performance GuideThe HCL OneDB™ Performance Guide describes how to configure and operate your HCL OneDB™ database server to improve overall system throughput and to improve the performance of SQL queries.
Table performance considerationsSome performance issues are associated with unfragmented tables and table fragments.
Managing extentsAs you add rows to a table, the database server allocates disk space in units called extents. Each extent is a block of physically contiguous pages from the dbspace. Even when the dbspace includes more than one chunk, each extent is allocated entirely within a single chunk, so that it remains contiguous.
Reclaiming unused space within an extentAfter the database server allocates disk space to a tblspace as part of an extent, that space remains dedicated to the tblspace. Even if all extent pages become empty after you delete data, the disk space remains unavailable for use by other tables unless you reclaim the space.

Reclaiming unused space within an extent

After the database server allocates disk space to a tblspace as part of an extent, that space remains dedicated to the tblspace. Even if all extent pages become empty after you delete data, the disk space remains unavailable for use by other tables unless you reclaim the space.

Important: When you delete rows in a table, the database server reuses that space to insert new rows into the same table. This section describes the procedures for reclaiming unused space for use by other tables.

You might want to resize a table that does not require the entire amount of space that was originally allocated to it. You can reallocate a smaller dbspace and release the unneeded space for other tables to use.

As the database server administrator, you can reclaim the disk space in empty extents and make it available to other users by rebuilding the table. To rebuild the table, use any of the following SQL statements:

ALTER INDEX
UNLOAD and LOAD
ALTER FRAGMENT