User Defined Collection (UDC) Creation Wizard
Use User Defined Collections when you have identified a specific activity of interest and the granularity level provided in the default system collection is insufficient.
The usefulness of UDCs as a performance monitoring tool is a function of how well the administrator knows the system's Oracle resources and (potential) bottlenecks. The ease and rapidity with which problematic behavior is identified and isolated depends on how well the critical dimensions are chosen.
For example:
A user reports performance problems every Thursday between 13:00 and 16:00. Use the UDC to fully monitor the user's activity down to the statement activity level.
Trace a known problematic SQL statement through an orientation of mutual effect of the SQL in response to tuning efforts (for example, index optimization or I/O optimization) and in this manner identify the specific effects and trends.