DSQSIROW (controlling the number of report rows retrieved for display)

Parameter name

DSQSIROW

Short form

F

Valid values

Any number from 0 through 99,999,999

Default

Minimum of 100 rows retrieved prior to the first report screen

Use DSQSIROW to specify the maximum number of rows QMF retrieves into the data object before displaying the first screen of the report to the user. DSQSIROW applies only to the initial load of a new data object, created by:

• Executing queries that use SQL SELECT statements
• Displaying a database table with the QMF DISPLAY command

To determine the proper value for this parameter, use step 1 of the algorithm in Estimating the space required for a spill file to estimate the size of a block of rows for the largest table a user is likely to query. A block is the number of rows that fit into one 4,096-byte buffer.

After every block of rows is retrieved, QMF compares the total number of retrieved rows to the value of DSQSIROW to determine whether to display the first screen of data. For example, suppose a block in your installation is 62 rows long, and you set DSQSIROW to 50. QMF retrieves 62 rows of data and, upon comparing 62 to 50, stops retrieving rows and displays the first screen of data.

Some report formatting options, such as percent (%) usage codes and ACROSS reports, require that all the data be retrieved before QMF displays the first screen. QMF ignores the DSQSIROW value in these situations. See the QMF Reference manual for more information about these formatting options.

Performance with small DSQSIROW values

If you use too small a value for DSQSIROW, QMF might not be able to complete the data object before the first screen of data is displayed. An incomplete data object causes share locks on the data, which can prevent other users from updating the data. DB2 maintains an EDM pool to service its requesters. While a data object is incomplete, the requester contends with all other requesters for EDM resources.

Many users might be affected if a QMF control table or a part of the system catalog is locked. You can release the locks in one of the following ways:

• Use the BOTTOM command to retrieve the remaining rows into the data object, then release the locks.
• Use the RESET DATA command to release these locks and clear the data object, whether or not all requested rows were retrieved.
• Use any SAVE command (for example, SAVE DATA or SAVE FORM) to retrieve and save the remaining rows into the data object, then release the locks.

To get the best performance in a noninteractive session (when the DSQSMODE parameter is set to B), use a value of 0 for DSQSIROW unless you want to minimize the number of open read locks while QMF is retrieving or formatting data.

Do not use DSQSIROW to limit the number of rows that QMF displays on the screen. Although you can specify a small value, QMF retrieves enough rows to fill the screen display in an interactive session.

Performance with large DSQSIROW values

If you use too large a value for DSQSIROW, QMF might take a long time to display the first screen of data. If you set DSQSIROW higher than you set the DSQSBSTG parameter, QMF might display a message indicating that there is insufficient storage available to satisfy the user's request.

When storage for the region is full, QMF waits for virtual storage to become available to finish retrieving rows for the database. When you plan your values for DSQSBSTG and DSQSIROW, remember that in CICS, QMF could time-out while waiting for storage to become available.