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

DO I = 1 TO 1000;
FETCH SENSITIVE NEXT C1 INTO
:COL1,:COL2,:COL3,:COL4,:COL5,
:COL6;
UPDATE TABLE SET COL6 = :COL6 +10 WHERE CURRENT OF C1;
END;
(Same for Deletes)
Example 3-17 shows the program of a dynamic scrollable cursor. This program specifies
explicitly DYNAMIC cursor in DECLARE CURSOR because the program is for update or
delete.
Example 3-17 Update program of dynamic cursor
DECLARE C1 SENSITIVE DYNAMIC SCROLL CURSOR WITH HOLD
FOR SELECT
COL1, COL2, COL3, COL4, COL5,
COL6 FROM TABLE
WHERE COL2 < ‘ROWNNNNNNNNN’
FOR UPDATE OF COL6;
DO I = 1 TO 1000;
FETCH SENSITIVE NEXT C1 INTO
:COL1,:COL2,:COL3,:COL4,:COL5,
:COL6;
UPDATE TABLE SET COL6 = :COL6 +10 WHERE CURRENT OF C1;
END;
(Same for Deletes)
As in the previous test case, we now examine UPDATEs and DELETEs with different
numbers of qualified rows. The summary description of this test case is:
► Use ISO(RS) as a bind parameter
This option protects data integrity (not for performance).
► 100k or 10 FETCHes followed by 100k or 10 UPDATEs
► 100k or 10 FETCHes followed by 100k or 10 DELETEs
► FETCH of 6 columns for a total of 37 bytes
► Qualified 1 M or 50k rows opened as a cursor
The trace record results for a static and dynamic updatable cursor are listed in Table 3-5.
Table 3-5 Update cursor static vs. dynamic
Trace data Static Dynamic
Class 1
ET/CPU
Class 2
ET/CPU
Class 3
suspend
UPDATE
or
DELETE
1k
Open 1M
UPDATE
or
DELETE
10
Open 1M
UPDATE
or
DELETE
1k
Open 50k
UPDATE
or
DELETE
1k
Open 1M
UPDATE
or
DELETE
10
Open 1M
UPDATE
or
DELETE
1k
Open 50k
16.44/11.51 15.75/11.16 4.95 / 1.33 0.601/0.148 0.218/0.016 0.508/0.144
16.43/11.49 15.75/11.16 4.93 / 1.32 0.589/0.135 0.215/0.014 0.496/0.131
4.5 4.31 3.56 0.454 0.195 0.364
Chapter 3. SQL performance 101