Implementing Siebel eBusiness Applications on DB2 UDB for z/OS and OS/390 > Maintenance Considerations for zSeries >

About Cursor Close

Cursor close allows you to regulate system resource utilization by Siebel clients in an z/OS and OS/390 environment by setting cursor configuration parameters.

The cursor configuration parameters specify the number of database rows a Siebel client cursor can get from a user-entered query or a Siebel operation that generates a SQL query.

The cursor configuration parameters, MaxCursorSize and PreFetchSize, are read at startup from the following places:

• Enterprise profile configuration parameters on the Siebel Server for Siebel Web Clients.
• Application configuration (.cfg) file for Siebel Dedicated Web Clients and Siebel Mobile Web Clients.

The Siebel client connector closes the SQL cursor after the number of rows specified by cursor close parameters DSMaxCursorSize and DSPreFetchSize have been retrieved. By default on other DBMS platforms, Siebel Systems sets DSMaxCursorSize and DSPreFetchSize to values of -1 and -1 which causes the cursors to remain open to retrieve additional data.

When using DB2 for z/OS and OS/390 v7, setting the values of the DSMaxCursorSize and the DSPreFetchSize parameters to -1 can cause a high number of DB2 Database Active Threads (DBAT); this can potentially lead to DB2 DBM1 address space task abends (abnormal ends) caused by DBM1 virtual storage constraints. To alleviate this problem, Siebel Systems has recommended setting the MaxCursorSize and PreFetchSize for zSeries customers to positive values. The default value for both MaxCursorSize and PreFetchSize is 128. This allows a reasonable number of rows to be retrieved without holding open the cursor. Once the cursor is closed, the change is committed and the Database Active Thread (DBAT) becomes inactive.

Siebel Systems recommends that your corporate IT department and Siebel administrator collaborate to determine the values for these parameters that are most appropriate for each class of users connecting to DB2 UDB for z/OS and OS/390. These guidelines are not mandated, but provide a balance between system resource utilization, user responsiveness, and productivity. Your enterprise might have unique requirements beyond the scope of this chapter. For assistance, contact Siebel Expert Services.