RAC Background Processes

RAC Background Processes

A.Lock Monitor Processes (LMON)
B.Lock Monitor Services (LMS)
C.Lock Monitor Daemon Process ( LMD)
D.LCKn ( Lock Process)
E.DIAG (Diagnostic Daemon)
F.ACMS:(Atomic Controlfile to Memory Service)--(from Oracle 11g)

A.Lock Monitor Processes (LMON)-

1.It is also called as  GES [Global Enqueue Service] monitor.
2.LMON Maintains GCS memory structures.
3.LMON handles the abnormal termination of processes and instances.
4.LMON deals with Reconfiguration of locks & resources when an instance joins or leaves the cluster (During reconfiguration LMON generate the trace files)
5.LMON Processes manages the global locks & resources.
6.LMON also provides cluster group services.
7.It checks for instance deaths and listens for local messaging.
8.Lock monitor co-ordinates with the Process Monitor (PMON) to recover dead processes that hold instance locks.

B.Lock Monitor Services (LMS)

1.It is also called the GCS (Global Cache Services) processes.
2.It consumes significant amount of CPU time.
3.It is the cache fusion part and the most active process.
4.Each node will have 2 or more LMS processes.
5.LMS also constantly checks with the LMD background process (or our GES process) to get the lock requests placed by the LMD process.
6.It is advised to Increase the parameter value, if global cache activity is very high.
7.It handles the consistent copies of blocks that are transferred between instances.

C. Lock Monitor Daemon Process ( LMDn)

1.It also monitors for lock conversion time outs.
2.LMD process performs lock and deadlock detection globally.
3.LMD process also handles deadlock detection and remote enqueue requests.
4.LMON-provided services are also known as cluster group services (CGS).

D.LCKn (Lock Process)

1.This process is called as instance enqueue process.
2.It manages instance resource requests & cross instance calls for shared resources.
3.During instance recovery, it builds a list of invalid lock elements and validates lock elements.
4.This process manages non-cache fusion resource requests such as library and row cache requests.

E.DIAG (Diagnostic Daemon)

1.A new background process introduced in Oracle 10g featuring new enhanced diagnosability framework.
2.Regularly monitors the health of the instance.
3.It is also checks instance hangs & deadlocks.
4.It captures the vital diagnostics data for instance & process failures.

F.ACMS:(Atomic Controlfile to Memory Service)--(from Oracle 11g)
1.ACMS stands for Atomic Control file Memory Service.
2.ACMS is a agent that help to ensure committed data written into the disk from SGA.