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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.
Monitoring the upper limit on extents and extent interleavingYou can monitor the upper limit on the number of extents. You can also check for and eliminate extent interleaving.
Checking for extent interleavingWhen two or more growing tables share a dbspace, extents from one tblspace can be placed between extents from another tblspace. When this situation occurs, the extents are said to be interleaved. Performance suffers when disk seeks for a table must span more than one extent, particularly for sequential scans.

Checking for extent interleaving

When two or more growing tables share a dbspace, extents from one tblspace can be placed between extents from another tblspace. When this situation occurs, the extents are said to be interleaved. Performance suffers when disk seeks for a table must span more than one extent, particularly for sequential scans.

Interleaving creates gaps between the extents of a table. Interleaved table extents shows gaps between table extents.

This figure is described in the surrounding text. — Figure 1: Interleaved table extents

Try to optimize the table-extent sizes to allocate contiguous disk space, which limits head movement. Also consider placing the tables in separate dbspaces.

Check periodically for extent interleaving by monitoring chunks. Execute oncheck -pe to obtain the physical layout of information in the chunk. The following information appears:

Dbspace name and owner
Number of chunks in the dbspace
Sequential layout of tables and free space in each chunk
Number of pages dedicated to each table extent or free space

This output is useful for determining the degree of extent interleaving. If the database server cannot allocate an extent in a chunk despite an adequate number of free pages, the chunk might be badly interleaved.