13.1.5 Preventing SQL statement execution wait status from occurring

This subsection explains how to improve processing performance by re-evaluating the number of processing real threads specified for the adb_sys_rthd_num operand in the server definition.

If the specified number of processing real threads is small, an SQL statement execution wait status might occur. When this wait status occurs for an SQL statement, processing of the SQL statement might take a long time. Therefore, check whether an appropriate number of processing real threads has been specified.

Procedure

1. Check the SQL statement execution wait status.

   Check the values of the following items in the HADB server statistical information that is output when the adbstat command is executed:

   • SQL_execute_wait_total_time (total SQL statement execution wait time)

   • SQL_execute_wait_cnt (number of times SQL statements waited for execution)

   If non-zero values were output to both SQL_execute_wait_total_time and SQL_execute_wait_cnt, an SQL statement execution wait status has occurred. In such a case, increasing the value specified for the adb_sys_rthd_num operand might prevent SQL statement execution wait status from occurring and improve processing performance in some cases.

2. Terminate the HADB server.

   Terminate the HADB server by executing the adbstop command.

3. Change the server definition.

   Increase the value specified for the adb_sys_rthd_num operand in the server definition to increase the number of processing real threads used by the HADB server.

   Important

   If you changed the value of the adb_sys_rthd_num operand, always re-estimate the memory requirements for the HADB server. For details about estimation of the HADB server's memory requirement, see 6.3 Estimating the HADB server's memory requirement.

4. Start the HADB server.

   Execute the adbstart command to start the HADB server.

Note

For details about the adb_sys_rthd_num operand in the server definition, see the description of the adb_sys_rthd_num operand in 7.2.2 Operands related to performance (set format).

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