After deciding whether the queue manager should use circular or linear logging, you need to estimate the size of the log that the queue manager needs. The size of the log is determined by the following log configuration parameters:
Table 17 shows the amount of data the queue manager logs for various operations. Most queue manager operations need a minimal amount of log space. However, when a persistent message is put to a queue, all the message data must be written to the log to make it possible to recover the message. The size of the log depends, typically, on the number and size of the persistent messages the queue manager needs to handle.
Operation | Size |
---|---|
Put persistent message | 750 bytes + message length
If the message is large, it is divided into segments of 15700 bytes, each with a 300-byte overhead. |
Get message | 260 bytes |
Syncpoint, commit | 750 bytes |
Syncpoint, rollback | 1000 bytes + 12 bytes for each get or put to be rolled back |
Create object | 1500 bytes |
Delete object | 300 bytes |
Alter attributes | 1024 bytes |
Record media image | 800 bytes + image
The image is divided into segments of 260 000 bytes, each having a 300-byte overhead. |
Checkpoint | 750 bytes + 200 bytes for each active unit of work
Additional data might be logged for any uncommitted puts or gets that have been buffered for performance reasons. |
If you do not define more primary log files than secondary log files, the queue manager might allocate secondary log files before a checkpoint is taken. This makes the primary log files available for reuse.
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