Chapter 5. SAP usage of LOBs 157
Table 5-7 dbsl_lib profile parameters for LOB handling (c) SAP AG; 2006
5.12 Performance measurements
Some measurement results are included here from different sources.
5.12.1 Locks and SELECT
The IBM/SAP performance team used the SAP program R3load (a utility often used to export
tables in SAP platform independent format) as a means to measure repeated workloads
against LOBs in DB2 V8 and DB2 9 subsystems. The tool is used to export records from a
table with a LOB column into a file and is executed on a remote network-connected client.
The purpose here is to evaluate the impact of the new locking mechanisms for LOBs in DB2 9
showing improvements in the context of a real workload.
The measurement data shows the improvements with reduced locking on LOB objects in
(c) SAP AG; 2006
Parameter Recommended value Description
64,000 bytes Size of the local LOB buffer. Minimum value
is 32,000 bytes, maximum 2,000,000 bytes.
1 Possible values are [0,1].
Use 0 to turn off the extended da feature.
0 Possible values are [0,1].
Use 1 to turn on the DB2 Connect CLI LOB
streaming. Not supported with DB2 V8.
20 Possible values [0,MAX_INT].
Use 0 to turn off chaining. For values
greater than 0, this number gives the
minimum value of rows which have to fit into
the dbsl_lib array buffer before chaining is
1,000 Possible values [0,MAX_INT]. Number of
locators to fit into free locator buffer. Set to
0 to turn off the free locator buffer.
1 GB Possible values [0,2048]. Threshold for
storage which locators in locator free buffer
can hold before freed.
0 Possible values [0,4].
0 corresponds to dbsl trace off.
1 corresponds to dbsl statement trace.
2 is unused.
3 corresponds to dbsl statement and data
trace, data is truncated.
4 corresponds to dbsl statement and data
trace, data is not truncated.
0 Possible values [0,1].
Set to 1 to turn on CLI trace.
Directory to which CLI traces should be
written. If not set, no CLI traces are written.