Which memory structure contains the information used by the server process to validate the user privileges?

The data dictionary cache is part of the System Global Area (SGA) that stores data dictionary information including user privileges, object definitions, and security attributes. When a server process needs to validate user privileges, it queries this cached information rather than accessing the physical data dictionary tables on disk, which significantly improves performance. The buffer cache stores database blocks, the library cache holds SQL and PL/SQL code, and the redo log buffer stores redo entries - none of these contain privilege validation data.