BufferPool Performance Analysis Beyond the Basic Hit Ratio.....

Data Collection Options:
- Performance Trace:
  - SMF Really Bad Choice, High Overhead
  - GTF Can you start one? Do you know how? High Overhead
- IFI Interface
  - Flat File Doesn’t Impact Others

Previous slide Next slide Back to the first slide View Graphic Version

Notes:

SMF is not a good destination for this type of trace data. DB2s usage of SMF is rather inefficient as a starting point, SMF is used very heavily by MVS, CICS, and other application and system software. Therefore, it is easy to flood the buffers and loose data. Other facilities use SMF data as input, such as MICS and MXG. This may cause these jobs to run out of work space and abend.

GTF is an MVS system level facility. If you have never used it, then forget about it. It has its own syntax, and has to be started either from the MVS console or by a system programmer. It also causes substantial overhead to DB2 because of the short record lengths and higher physical I/O rates.

By using the IFI interface, and writing to a dataset, the standard and instrumentation headers can be thrown away. This reduces the amount of data written by 200 bytes. The actual data records we need are quite short as you will see.