Figure 3-16. Second part of the pseudocode for when a process asks for a mutex. The Fast_Get function is shown, along with the shared and exclusive mode request details.

The mutex Fast_Get function objective is the same as the latch Fast_Get function, but since mutexes are being used, the Fast_Get function can make use of the built-in and extremely quick mutex capabilities. Figure 3-17 illustrates a model of a mutex and its memory structure. If you look closely at Figure 3-17, you can see the mutex has been defined as part of the memory structure MS1. The memory structure contains two mutex variables: the holder identifier and the reference count. If an Oracle session is holding the mutex exclusively or is in the middle of running the Fast_Get function, the holder identifier contains its session identifier (v$session.sid).

Figure 3-17. A model of a mutex and its memory structure. Notice this mutex is part of the memory structure MS1. The memory structure contains the mutex inherent holder identifier and reference count variables, and also the actual memory structure itself.