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

FETCH
FROM
Figure 3-45 FETCH syntax
INSENSITIVE
SENSITIVE
single-fetch-clause: ,
These are implications on the FETCH statement using dynamic scrollable cursors:
► The keyword INSENSITIVE is not allowed (SQLCODE -244) in the FETCH statement:
– If the associated DECLARE CURSOR statement is specified as SENSITIVE DYNAMIC
SCROLL, or
– If the associated DECLARE CURSOR statement is specified as ASENSITIVE
SCROLL, and DB2 selects SENSITIVE DYNAMIC SCROLL for the associated
SELECT statement.
► SQLCODE +231 is returned in special cases
– If FETCH CURRENT or FETCH RELATIVE +0 are requested, but the row on which the
cursor is positioned has been deleted or updated so that it no longer meets the criteria.
It happens only when using ISOLATION(CS) and CURRENT DATA(NO), which allows
the row retrieved without taking locks.
Data concurrency in dynamic scrollable cursors
The characteristic of using dynamic scrollable cursors is that you can see immediately the
newly updated or inserted or deleted data of your application. To get maximum data
concurrency and get a high performance, you should use CURRENTDATA(NO) as a bind
option and ISOLATION(CS) as an ISOLATION level.
CURRENTDATA is a bind option which helps to determine the currency of data returned by
an application cursor. In a local environment, CURRENTDATA can only have an impact for an
application bound with ISOLATION(CS) and executing read-only queries which do not utilize
a work file. The primary benefit in using CURRENTDATA(NO) is performance. This is
especially true in a data sharing environment; using CURRENTDATA(NO) should reduce lock
contention and CPU utilization.
96 DB2 UDB for z/OS Version 8 Performance Topics
FETCH syntax
cursor-name
INTO host-variable
INTO DESCRIPTOR
NEXT
PRIOR
FIRST
LAST
CURRENT
BEFORE
AFTER
ABSOLUTE host-variable
integer-constant
RELATIVE host-variable
integer-constant
descriptor-name
single-fetch-clause
No new syntax.
Cannot specify
INSENSITIVE -
SQLCODE -244