Oracle Enterprise Manager (EM) reports on many security policies when they are violated. One of them are about execute privileges on standard PL/SQL packages granted to PUBLIC. One a day this summer with nothing better to do I went on to revoke these privileges. The wages for my efforts was several ORA-600 errors:
ORA-00600: internal error code, arguments: [qmxqtmChkXQAtomMapSQL:2], , , , , , , , , , , 
00600. 00000 - “internal error code, arguments: [%s], [%s], [%s], [%s], [%s], [%s], [%s], [%s]”
*Cause: This is the generic internal error number for Oracle program
exceptions. This indicates that a process has encountered an
*Action: Report as a bug - the first argument is the internal error number
A quick research on My Oracle Support indicated that some standard packages depends on these privileges granted to PUBLIC. The solution is to grant back to PUBLIC if you are in a hurry, or grant the privilege to the owners of the individual packages (like XDB). The errors continued after the granting was done, but stopped after I bounced the database instance.
Just because EM reports something and the solution seems obvious, it is not alway wise to apply remedy immediately, especially in production. It surprised me a little that EM suggests a security policy that Oracle’s own packages do not adhere to.