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4.15.8 Special considerations for large objects (LOBs)
Business Process Manager workloads often use LOBs to store data. For Oracle databases,
LOBs are most efficiently handled by using the file system cache, while other database
activity is more efficiently managed by using concurrent I/O. So, to achieve optimal
performance, the LOBs must be managed separately from other I/O activity. Use the following
approach to achieve this performance:
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Disable concurrent I/O at the database level. For example, for AIX set filesystemio_options
to asynch.
Move the LOBs to separate file systems.
Mount all file systems that do not have LOBs using concurrent I/O.
Partition the LOB table spaces to reduce file locking contention.
Also for LOBs, enable caching for LOB columns for the lsw_task_execution_context and
lsw_bpd_instance_data tables
4.15.9 Setting prepared statement cache size
Prepared statements that are cached perform faster than those not cached. However, for
Oracle databases, each prepared statement can take a significant amount of Java heap
space (140 KB per statement for some cases that we have seen in Business Process
Manager solutions). As such, do the following tasks:
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Judiciously set prepared statement cache sizes to be large enough to improve
performance (particularly for the BPEDB data source for BPEL business processes, which
realize significant benefit from the prepared statement cache).
Monitor Java heap utilization to ensure that the prepared statements are not using too
much heap space or causing OutOfMemory exceptions.
4.15.10 Specific tuning parameter recommendations
For our internal performance evaluation of the Business Process Manager 8.0 Process
Server, we changed the following Oracle database settings from their default. This approach
is a useful starting point for tuning the Oracle database, but follow the suggested
methodology for your applications and configuration. The first four settings in the following list
generally vary by workload and volume, so consult with your database administrator to
determine appropriate values. Also, the last two settings work well for Business Process
Manager solutions where the Oracle undo operation is typically not used, but might not work
well for non-Business Process Manager databases.
► memory_max_target: 25G
► memory_target: 25G
► processes: 500
► open_cursors: 1000
► undo_retention: 200
► _undo_autotune: FALSE
Also, edit the 98database.xml file in the profiles configuration directory, and change the
following parameter to keep more threads active in the connection pool to better manage
peak throughput.
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90 IBM Business Process Manager V8.0 Performance Tuning and Best Practices