SharePlex 11.3 - Installation and Setup Guide

SharePlex caches frequently-used SQL statements for reuse so that they do not have to be parsed and bound every time they recur. This is an adjustable feature of SharePlex that is named SQL Cache. You can tune this feature to maximize its advantages based on the amount of repetitive statements your application generates.

SQL Cache improves the performance of Post only if the same SQL statements are issued over and over again, with no variation except the data values. If that is not true of your environment, then SQL Cache adds unnecessary overhead to the Post process, and you should disable it.

Supported targets

All

Enable or disable SQL Cache

Control SQL Cache as follows:

Oracle

Parameter	Description
SP_OPO_SQL_CACHE_DISABLE	Enables or disables SQL Cache. Enabled by default with a setting of 0. To disable SQL Cache set the parameter to 1. To disable SQL Cache only for batch operations set the parameter to 3, which reduces the amount of memory that Post uses.
SP_OPO_MAX_CDA	Determines the number of active statements to cache per Post session. Post opens 50 cursors per session by default. You can increase or decrease this setting if needed. For more information, see Adjust Open Cursors.

Open Target

Parameter	Description
SP_OPX_SQL_CACHE_DISABLE	Enables or disables SQL Cache. Enabled by default with a setting of 0. To disable SQL Cache set the parameter to 1.
Use the target command: target r.database [queue queuename] set resources max_active_statements=number_of_active_statements	Determines the number of active statements to cache per Post session. For Open Target databases, Post gets the number of allowed active statements from the ODBC driver. If that value is lower than the setting for max_active_statements, Post stops and returns an error. You can either disable the SQL Cache feature or reduce the value of max_active_statements.

Parameter

Description

SP_OPX_SQL_CACHE_DISABLE

Enables or disables SQL Cache. Enabled by default with a setting of 0. To disable SQL Cache set the parameter to 1.

Use the target command:

target r.database [queue queuename] set resources max_active_statements=number_of_active_statements

Determines the number of active statements to cache per Post session. For Open Target databases, Post gets the number of allowed active statements from the ODBC driver. If that value is lower than the setting for max_active_statements, Post stops and returns an error. You can either disable the SQL Cache feature or reduce the value of max_active_statements.

Tune SQL Cache for best performance

Follow these steps to make certain that the number of active statements is optimal for the operations that are replicated.

Determine the hit ratio for cached statements by running sp_ctrl and issuing the show post detail command.
Look for the SQL cache hit count field. It shows the ratio of the total number of messages that are executed without parsing and binding divided by the total number of INSERT, UPDATE and DELETE operations. For example, a hit ratio of 36% indicates that Post is using cached statements 36 percent of the time.
View the hit ratio after several days of typical replication activity to gauge the ideal setting for the number of active statements. If the hit ratio is under 50 percent, increase the parameter value in a small increment of about 5 statements.
Monitor the hit ratio over the next few days. If the hit ratio increases, it means your applications are using all of the cursors allowed for active statements. Continue to increase the parameter value in small increments until the hit ratio remains constant.

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