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Problem(Abstract)
IBM® Informix Server™ may Assert Failed showing messages such as "log_put( OLDRSAM:66, 35052): log record too long" in the with Assert Failed File and/or "Checkpoint log record may not fit into the logical log buffer. Recommended minimum value for LOGBUFF is 36" in the online.log file.
Resolving the problem
PROBLEM
There is an undocumented limitation in IBM® Informix Server™ that sets the maximum number of transactions opened at checkpoint time. If this limit is exceeded, the instance will stop
If the number of open transactions open at checkpoint time exceeds certain number (This number is dependant of the Logical Log Buffer Size), the instance will stop. You can check that the Assert Failure File will show this message:
- 14:51:48 log_put( OLDRSAM:66, 35052): log record too long
logrec
Bc87a2044: 000088ec 00000042 00000010 00000000 .......B ........
Bc87a2054: 00000001 01c72018 09bae247 00000000 ...... . ...G....
Also you will notice some warnings in the online.log before the instance stops with the following messages:
- 15:24:55 Checkpoint log record may not fit into the logical log buffer.
Recommended minimum value for LOGBUFF is 36.
CAUSE
Informix Server uses the Logical Log Buffer (LLB) to write logical log records (LLR) to the Logical Log File. A logical Log record cannot be bigger than the LLB, if such a situation is found, the engine will abort to prevent an incomplete write to the Logical Log File.
Usually, LLR are very small compared with a 32KB buffer size (The default LLB size), however the size of a checkpoint record depends on the number of transactions opened at checkpoint time. In version 9.4 the space required by a Checkpoint Logical Log Record will be :
- 36 + 24xN bytes
where N is the number of transactions open at that moment.
A 32KB Logical Log Buffer size will allow for only 1363 open transactions at checkpoint time. If that number is exceeded, the engine will crash.
SOLUTION
Increase the Logical Log Buffer to a higher value. The formula given above is for version 9.4 but can be used for any version as the sizes of the structures do not change that much.
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