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Profiling filters out well performing, light weight SQL and collects information on heavy weight SQL. SQL that is heavy weight is either long running queries or queries that are short but run so often that they put load on the database
Profiler takes snapshots of user and session activity once a second and builds up a statistical model of the load on the database. The sampled data is displayed in three ways:

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Details of profiling sessions can be saved to an .oar file, which you can access through the SQL Project Explorer, or if you are profiling to an Oracle 9i, 10g, or 11g data source, you can see the profiling sessions in the Profiling Repository node of the data source in the Data Source Explorer, or in the Profiling Repositories node. Profiling direct to a repository means the session details are sent directly to the hard disk of the data source. If you have enough free disk space, you can collect data for a longer time than if you were profiling to a file which accumulates in memory until you save the session to disk.