Cursor Close Parameter Values on DB2 for z/OS

By default, on other DBMS platforms, Siebel CRM sets both MaxCursorSize and PreFetchSize to a value of -1, which causes the cursors to remain open to retrieve additional data.

On DB2 for z/OS, setting the value of the MaxCursorSize parameter to -1 can cause a high number of DB2 Database Active Threads (DBAT); this can potentially lead to DB2 DBM1 address-space task abnormal ends, caused by DBM1 virtual storage constraints. To alleviate this problem, it is recommended that z/OS users set the MaxCursorSize parameter to a positive value. (Siebel CRM on DB2 for z/OS ignores values specified for the PreFetchSize parameter.)

The minimum acceptable value that you can specify for the MaxCursorSize cursor close parameter is 32; the default value is 128. This value allows a reasonable number of rows to be retrieved without holding open the cursor. After the cursor is closed, the change is committed and the Database Active Thread (DBAT) becomes inactive.

Note: The default value of the MaxCursorSize parameter for Siebel Tools is -1; because the number of Siebel Tools users is relatively small, the number of active connections at any time is unlikely to exceed the DB2 for z/OS limit.

It is recommended that your corporate IT department and Siebel CRM administrator collaborate to determine the value for the cursor close parameter that is most appropriate for each class of users connecting to DB2 for z/OS. Guidelines are outlined in the following table; these are not mandated, but they provide a balance between system resource utilization, user responsiveness, and productivity. However, your enterprise might have unique requirements beyond the scope of this chapter.