Simulating buffer pool behavior

This topic describes how to simulate buffer pool behavior on the client.

About this task

Related tasks:
  • Before you can use this function, you must have performed the tasks described in:
    • Collecting data. The collected data can be made available for the simulation function in uncompressed or compressed format.
    • Downloading files from the host to the client

      A trace data file must be available on the client (the file with the recommended file name extension trace, or terse if compressed).

General remarks:
  1. Your client should have approximately 40 MB of available physical memory (random access memory) for this function. You can check this in the Windows Task Manager. Close other applications, if you receive an Out of memory message.
  2. The data used for this function reflects the buffer pool activity for the interval for which trace data was collected.
  3. Data used for simulations must be collected with short record format, continuously, and should have a record lost rate of less than 2%. If required, see Configuring a collect task and Interpreting trace status summary and trace messages for more details.
  4. The simulation function can handle trace data files of up to 2 GB.

    This size limit pertains to compressed and uncompressed trace data files. Uncompression requires additional time when a compressed trace data file is opened. Uncompression does not require additional disk space because uncompressed data is directly written into memory.

  5. The time to preprocess the trace data file and the time to perform a simulation very largely depends on the number of active objects in the trace data file, the number of different buffer pools, and the buffer pool sizes to be simulated. Note that a compressed trace data file contains approximately four times as much data than an uncompressed file.

    Example: On a 2.4 GHz client, a 1 GB trace data file takes roughly 1.5 minutes to be preprocessed and approximately five minutes to simulate four buffer pools from 25 000 to 1 000 000 pages (40 sizes). Note that a simulation runs considerably slower if other tasks are using the processor at the same time.

  6. If you want to print the simulation results shown in your web browser, use your browser's printing capabilities to print the information. For colored printouts, check the browser settings.

    Example: In the Internet Explorer, click Tools —► Internet Options —► Advanced. Under Printing, select Print background colors and images.

  7. In DB2® Performance Expert for z/OS®, you can configure a different web browser. If required, click Monitor —► Configuration —► Preferences and follow the instructions.