When mutexes are available, they are enabled. They can be disabled by setting the instance parameter _kks_use_mutex_pin to false. If your system is experiencing a deep mutex problem, Oracle support may advise you to turn off mutexes until a patch or two has been applied.

Most Oracle sites will never experience mutex contention and if they do, the stress will probably be related to pinning a cursor in either shared or exclusive mode.

Interestingly, for mutexes to operate, the operating system must support the compare and swap (CAS) operation. Reduced instruction set computer (RISC) operating systems, such as AIX or PA-RISC, may have chosen to reduce their instruction set by eliminating the CAS operation. In situations like these, Oracle will simulate the CAS operation by using a pool of latches (1,024 by default in Oracle Database 11g Release 1). The latches are named KGX, and their number can be changed by altering the instance parameter _kgx_latches. Obviously, this is not optimal for performance, but one hopes the net result will be beneficial.