Management of Informix Database Growth (SAP Library - SAP Database Guide: Informix (BC-DB-INF-DBA))

Management of Informix Database Growth

Purpose

This section provides information on how to manage the growth of your Informix database. If database objects (that is, dbspaces or tables) fill, you get error messages and the SAP System might stop processing. Therefore, it is always better to plan in advance for database growth, so anticipating problems before they occur.

Note

If your database has space management problems, alerts are raised in the Release 4 alert monitor in the Computing Center Management System (CCMS) of the SAP System. For more information, see Monitoring the Database with the Release 4 Alert Monitor (Informix).

Aim for the following goals:

To install the database in the best possible way with the available disks, while meeting anticipated future requirements. Refer to Database Setup for Production and the installation documentation listed at the end of this section.

To have enough disk space available for natural database growth by keeping a close watch on database expansion. The Informix database server does not dynamically allocate new space on disk. If the available space (including the space allowed for expansion at the table level) fills up, applications run into errors when they try to insert data. Refer to Database Growth Monitoring.

To avoid unnecessary fragmentation of dbspaces by ensuring that when you extend a dbspace, you add a sufficiently large chunk to accommodate future growth (at least in the medium term). Refer to Extension of a Dbspace.

To obtain optimal I/O load balance so that applications needing access to database data on disk do not experience degraded response times. Refer to Recognition of Space Problems and Errors.

A dbspace can only use its own chunks for storage data. This means that, if the chunks for one dbspace fill up, application errors due to lack of space might occur, even though there is free space available in other dbspaces. The Informix database server cannot dynamically extend a dbspace – this is your job as administrator. At the table level, expansion occurs dynamically as required but only up to a certain limit. You need to intervene if a table has been repeatedly extended and is approaching the maximum possible number of extents.

Process Flow

You size the dbspaces correctly before going live, in view of anticipated data storage requirements. If you get this right, you can avoid a lot of problems in the future. Refer to Database Setup for Production and the installation documentation listed at the end of this section.

You monitor the dbspaces and tables during live operation, identifying trends as early as possible. You need to monitor both storage and I/O to optimize dbspace management. Refer to Database Growth Monitoring.

You react in good time to avoid running out of space. This means adding chunks to dbspaces or reorganizing tables. Refer to Extension of a Dbspace.

You identify, diagnose and correct problems where I/O performance is degraded or storage space is running low. Refer to Recognition of Space Problems and Errors.

Some of the above goals might not be clear or might conflict with one another. As with any tuning operation, you have to balance the competing demands with the constraints of your particular site. Be sure to gather enough information before you make your change.

Result

Professional management of database growth increases the availability of your SAP System. Be sure to monitor any changes you make. Refer to Database Growth Monitoring.

See also:
R/3 Installation on Windows NT – Informix Database
R/3 Installation on UNIX – Informix Database