Best Practices for SAP BI using DB2 9 for z/OS - IBM Redbooks

the F- fact table, the E- fact table reference point can be accessed directly for
current data, thus improving query performance.
There is one exception when SAP compression can be omitted. This is the
case when you are using the SAP BIA and when the compression ratio is less
than 1.5.
7. Use fast deletion of table partitions.
Apply SAP note 894045 to activate the fast deletion of table partitions for
partitioned PSA and F- fact tables.
8. Partition E-Fact and F- fact tables.
The E- fact table (result of SAP compression) can be partitioned via SAP
cube maintenance, which provides greater opportunity for improved query
performance and elapsed time, and also potential reduction in operational
costs.
Partitioning the E- fact table increases the opportunity for DB2 parallelism,
which can significantly reduce the query elapsed time. Similarly, queries with
time-based filtering will be able to eliminate unnecessary partitions from being
accessed regardless of the filtering dimensions or indexes chosen for fact
table access. These two benefits also result in greater access path stability
for queries against the InfoCube.
The F- fact table will be automatically partitioned by request by setting a
RSADMIN parameter. In addition to improving query performance, this
significantly speeds up the deletion of a request and the RUNSTATS. Details
are in SAP note 860830.
An additional benefit of partitioning is the ability for partition level operations
such as COPY utility, REORG, or RUNSTATS to be invoked by the DBA.
With time-based partitions, historical partitions do not require further
REORG/RUNSTATS because their data will not change over time. An
increase in E- fact table size should not result in a significant increase in
operational maintenance costs.
For these reasons we recommend partitioning the E- fact tables and using
InfoCube compression.
9. Use DB2 HW compression.
DB2 hardware compression is one of the strengths that differentiates DB2 on
System z from other platforms. Compression rates of 70% and greater are
possible for large SAP BI objects, such as fact tables, data store objects, and
large aggregates. The four main benefits of compression include:
– Reduced disk space
– Improved elapsed time for sequential processing (for example, queries,
copy utility)
32 Best Practices for SAP BI using DB2 9 for z/OS