Synchronization point dump files

Question: Why is the KFPS02179-I message being issued repeatedly (this message says that the time for collecting a synchronization point dump has been reached, but collection of the dump was skipped because the previous synchronization point dump processing had not been completed)?

Answer

This message is output in the following cases:

The system log file swapping interval is too short.
The UAP's transaction execution time is longer than the synchronization point dump acquisition interval.
Synchronization point dump acquisition is being delayed by deferred write processing.

If this message is output frequently, take the appropriate action described below, according to the factor code:

For factor code = A01-01
Take the action prescribed in 23.3 Tuning the synchronization point processing time when deferred write processing is used.
For factor code = A01-02
A transaction that was uncompleted when the previous synchronization point dump was acquired has not yet been completed. This is the case because the UAP's transaction execution time is longer than the synchronization point dump acquisition interval. Take the action prescribed in the KFPS04374-I message, which is output next. If this message is output even after you have taken the action, follow the instructions below under All other cases.
All other cases
Increase the value specified in the pd_log_sdinterval operand. Alternatively, increase the size of the system log file. If the message is still output frequently, consider revising the UAP. That is, divide a transaction with a long execution time into multiple transactions so that the execution time per transaction is shorter.

Even when this message is output, you can continue or restart online operations if there are a sufficient number of system log files that can be used as swappable targets. However, restarting HiRDB might take longer.

If there are enough generations and there is enough space in the system log file, HiRDB or the unit might terminate abnormally due to a shortage of overwrite-enabled system log files (the KFPS01256-E message is issued). To avoid such problems, reevaluate the following:

When it takes a long time for the transaction to commit after updating a database or data dictionary

Evaluate the following items:

Would it be possible to issue the commit statement during the processing?
If the transaction retrieves a large amount of data after updating, would it be possible to reduce the time from the first update processing in the transaction to the commit point by changing the sequence of the update processing and the retrieval processing?

When there is insufficient space in the system log file or too few generations

Evaluate the following items:

We recommend that you provide the amount of file space necessary to store system logs that will be output during operation of HiRDB. If this is not feasible, try to allocate at least the size recommended in the HiRDB Version 9 Installation and Design Guide.
Do not collect a database update log for a transaction that updates a large amount of data. Whether a database update log is to be collected is specified in the PDDBLOG operand in the client environment definition. If a database update log is not collected and an error occurs during UAP execution, the database can be restored only to the point where its backup was made.

Question: What is meant by the number of guaranteed valid generations of the synchronization point dump file?

Answer: Information such as a read operation's starting point in the system log file is acquired in the synchronization point dump file; this information is useful in the event a restart of HiRDB becomes necessary. Thus, the portion of the system log file beginning at the location indicated in the synchronization point dump file is write-protected because it might be needed for a restart.; The number of guaranteed valid generations is the number of generations of synchronization point dump files that are used to write-protect the system log file. In other words, if the number of guaranteed valid generations is 1, only the system log file corresponding to the most recent synchronization point dump file is write-protected. If the number of guaranteed valid generations is 2, the system log file corresponding to the most recent synchronization point dump file and the one immediately preceding it are write-protected. Therefore, if the number of guaranteed valid generations is 2, the number of system log files that are write-protected might increase.; The number of synchronization point dump file guaranteed valid generations is specified in the pd_spd_assurance_count operand.

Appendix A.2 Synchronization point dump files

(1) The KFPS02179-I message is issued repeatedly

(2) Number of guaranteed valid generations