Space Management with Informix

Purpose

This section looks at space management (including reorganization) of database objects (that is, tables and dbspaces). If you neglect space management, this can lead to downtime due to normal database growth when database objects fill up. If this happens, applications cannot write to the database and you have to quickly make more space available. You might need to bring down the SAP system to tune and configure the database. Therefore, it is much better to anticipate the problem by monitoring and pro-actively managing the disk space in your database.

SAP recommends you to manage space on your Informix database using the Computing Center Management System (CCMS) in the SAP system and SAPDBA. You need to monitor regularly and occasionally take timely action to avoid the problem leading to downtime.

The problems of extent overflow, dbspace overflow, and a high number of extents for a table are more likely to occur in some dbspaces than in others. The following dbspaces in an SAP system are most likely to cause problems:

Dbspace

Comment

PSAPBTAB

Transaction data tables. Objects in this dbspace might expand very rapidly.

PSAPSTAB

Master data tables. Objects in this dbspace might expand very rapidly

PSAPCLU

Clustered tables, such as financial tables. Objects in this dbspace might expand very rapidly

PSAPPOOL

Pool tables, containing customization tables

PSAPPROT

Spool (that is, print) requests, protocols

Pay special attention to the following dbspaces in certain circumstances:

·        PSAPSOURCE, PSAPLOAD and PSAPDDIC

If you develop many new ABAPs, monitor these dbspaces closely.

·        PSAPTEMP

If you are running a large import or reorganization, you should closely watch this dbspace since it is used to store temporary data.

Process Flow

...

       1.      You manage extents.

       2.      You manage dbspaces, especially problematic ones.

       3.      You manage tablespaces.

       4.      You manage chunks.

       5.      If necessary, you reorganize tables, indexes, or dbspaces.

SAP recommends you to avoid reorganizations wherever possible. You can achieve this by correct configuration and sizing of the database together with proper monitoring.

Only reorganize with a clear justification. One such justification is that database objects might soon reach the maximum available size limits (that is, number of extents).

Result

By managing the space in your Informix database, you can avoid unplanned downtime due to database objects filling up.

See also:

Management of Informix Database Growth