13.1.9 Re-evaluating the trigger size for reducing user log files

This subsection explains how to improve processing performance by re-evaluating the trigger value (specified for the adb_log_usrfile_size operand in the server definition) for reducing the size of user log files.

When the update transaction is settled, the size of a user log file used by that update transaction might be larger than the size specified for the trigger value for reducing the size of user log files. In this case, the HADB server reduces the size of the user log file to the initial size. An increase in the number of times the user log file size is reduced to the initial size might affect update performance. Therefore, perform the following procedure to re-evaluate the value specified for the adb_log_usrfile_size operand.

Procedure:

1. Check the number of times the user log file size was reduced to the initial size.

   Check the following item in the information that is output when the adbstat command is executed:

   • Log_usrfile_reduced_cnt (the number of times the user log file size was reduced to the initial size)

   Note

   For details about the adbstat command, see adbstat (Perform Statistical Analysis of the HADB Server) in the manual HADB Command Reference.

2. Re-evaluate the value specified for the adb_log_usrfile_size operand.

   A large value output to Log_usrfile_reduced_cnt that you checked in step 1 indicates that the user log file size was reduced to the initial size many times. In this case, we recommend that you increase the following values specified for the adb_log_usrfile_size operand in the server definition:

   • Initial size of user log files

   • Trigger value for reducing the size of user log files

   As the preceding specification values increase, the number of times the user log file size is reduced to the initial size decreases.

   Tip

   In the execution result of the adbstat command, the value output under Log_usrfile_max_size indicates the maximum size of user log files during normal operations. We recommend that you specify, as the trigger value for reducing the size of user log files for the adb_log_usrfile_size operand, the value obtained by multiplying the preceding value by 1.5 to 2 as a safety factor. This enables you to perform processing for reducing the size of user log files only when the database is massively updated (for example, by an unscheduled operation).

3. Terminate the HADB server.

   Terminate the HADB server by executing the adbstop command.

4. Change the server definition.

   Increase the following values specified for the adb_log_usrfile_size operand in the server definition:

   • Initial size of user log files

   • Trigger value for reducing the size of user log files

5. Start the HADB server.

   Execute the adbstart command to start the HADB server.

Note

For details about the adb_log_usrfile_size operand in the server definition, see the adb_log_usrfile_size operand in 7.2.3 Operands related to system logs (set format).

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