Collecting I/O usage information tells you where your
  application is performing I/O operations, and gives
  detailed information on each I/O operation it records.
  Collecting I/O information can give you more detailed
  information than you can get from collecting system
  services information.

  To collect I/O usage information on your application:

  o  Compile and link your application with the PCA
     Collector

  o  Run your application. This causes the PCA Collector
     to take control of your application. PCA diplays the
     Collector main window on your screen.

  o  From the File pull-down menu, create a data file
     into which the Collector places performance data.

  o  Choose the I/O Usage query category.

  o  Click on the specific I/O query you are interested
     in getting information on.

  o  Click on Collect in the Collector main window.

  For information on displaying the results of the I/O
  Usage queries, refer to:

  o  The hardcopy manual, Guide to DIGITAL Performance
     and Coverage Analyzer for OpenVMS Systems

  o  The online help for the PCA Analyzer.