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

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Alternatively, if temporary trace is permitted <strong>for</strong> individual analysis, there is an<br />

<strong>SAP</strong> profile parameter stat/tabrec that can be activated to get more statistics on<br />

table access or transactions. You can change the online parameter stat/tabrec,<br />

which specifies the maximum number of table access statistics subrecords that<br />

the kernel can write <strong>for</strong> each transaction step. The N tables with the highest DB<br />

request time <strong>for</strong> each dialog step are stored.<br />

If you only want to activate the table access statistics <strong>for</strong> specific transactions,<br />

you can specify a maximum of five transactions in the online parameters<br />

stat/tcode1 to stat/tcode5. The table access statistics are then only produced <strong>for</strong><br />

these transactions.<br />

After tracing is done, it should be set to 0 (zero) at all times. Otherwise, the<br />

number of statistics records rises greatly, which can lead to per<strong>for</strong>mance<br />

problems in the statistics collector.<br />

To change parameter/tabrec online:<br />

1. Start the workload monitor by calling transaction ST03.<br />

2. Choose Expert → User Mode.<br />

3. Choose Collector & Perf. Database → Statistics Records and File →<br />

Online Parameters → Dialog Step Statistics.<br />

4. The system displays the Change Runtime Parameters <strong>for</strong> Statistics Collection<br />

dialog window.<br />

To look at table access statistics:<br />

1. Start the workload monitor by calling transaction ST03.<br />

2. Choose the user mode.<br />

3. In the Workload tree, choose the instance to be analyzed and the time period.<br />

4. Choose Analysis Views → Table Access Statistics.<br />

At this point, in<strong>for</strong>mation from ST03, RSMO, RSPC, and STAD transactions<br />

should provide you with a general idea of where the potential cause is. Now what<br />

can you do to alleviate it?<br />

If extraction takes the most elapsed time<br />

For this condition you can do a few things on the source data and source system<br />

to improve extraction. Source data can be from an earlier system, flat file, or R/3<br />

system. Generally, these are beyond your control, especially an earlier system,<br />

which may have slow disks, not enough CPUs, and less memory. However, you<br />

can have some influence on loading from a flat file and from a R/3 system, as<br />

described here.<br />

Chapter 8. Query and Load per<strong>for</strong>mance 153

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