DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

In an application, multi-row inserts, positioned updates, and positioned deletes have the
potential of expanding the unit of work, for instance by deleting a rowset. This can affect the
concurrency of other users accessing the data. Minimize contention by adjusting the size of
the host variable array, committing between inserts, updates, and preventing lock escalation.
GET DIAGNOSTICS can be used in conjunction with and instead of the SQLCA to interrogate
the results of all SQL statements. It is especially important when dealing with non-atomic
multi-row insert statements, and objects with long names, which potentially no longer fit into
the SQLCA message area. See DB2 UDB for z/OS Version 8 SQL Reference, SC18-7426-01
for details.
3.1.3 Multi-row fetch/update and multi-row fetch/delete in local applications
When the cursor is positioned on a rowset, the rows belonging to the rowset can be updated
or deleted:
► Multi-row FETCH/UPDATE
– Positioned UPDATE of multi-row FETCH
– The rows of the current rowset are updated if the cursor is positioned on a rowset
► Multi-row FETCH/DELETE
– Positioned DELETE of multi-row FETCH
– The rows of the current rowset are deleted if the cursor is positioned on a rowset
If cursor CS1 is positioned on a rowset consisting of 10 rows of a table and we want to delete
the fourth row of the rowset:
EXEC SQL DELETE FROM T1 WHERE CURRENT OF CS1 FOR ROW 4 OF ROWSET;
The same is applicable to UPDATE.
Example of usage of multi-row fetch/update and fetch/delete in PL/I
The example in Figure 3-3 shows the statements to update and delete rowsets of 10 rows
from a table positioned by a rowset cursor.
Chapter 3. SQL performance 33