Managing Chunks (Informix)

Use

You need to manage the chunks of your Informix database to avoid "chunk overflow". Chunks are the physical storage units used to build dbspaces. To extend a dbspace, you add chunks at the physical level.

If a large number of small chunks are created, it is possible that the Informix server limit for the maximum number of chunks in the database could be reached. The limit is either 2048 or the maximum number of open files per process, as allowed by your operating system (refer to the appropriate documentation). However, note that the limit is rarely reached.

If chunk overflow occurs, you have to reorganize and downtime occurs. Therefore, monitor your chunks to avoid this situation.

Procedure

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       1.      Monitor the number of chunks for your database regularly.

Refer to Listing Chunks with SAPDBA.

       2.      When creating new chunks, make sure that they are large enough.

Make sure that chunks are large enough to accommodate foreseeable growth in the dbspace. Otherwise, you have to repeat the procedure in the near future and the result is a large number of small chunks, with the danger of chunk overflow.

Refer to Adding a Chunk with SAPDBA.

       3.      If approaching chunk overflow, reorganize problem dbspaces with their tables.

With Informix databases, you do not need to regularly reorganize. However, if you are approaching the Informix server limit for the maximum number of chunks, this is a good reason to reorganize.

Use SAPDBA to identify dbspaces that consist of more than one chunk (see the first step above). Then you can use SAPDBA to reorganize these dbspaces so that they have fewer chunks, if possible just one chunk. Refer to Reorganizing a Dbspace and Its Tables with SAPDBA.

Result

You avoid chunk overflow and so avoid downtime for your Informix database and the SAP system.