Oracle RAC Background Processes And Single Instance

To check backgroup process

select name,description from V$bgprocess;


RAC specific background processes for the database instance :

LMSn
LMON
LCK0
LMDn
DIAG
RBAL
ASMB
RMSn
RSMN


LMSn (Global cache service monitor ) :coordinate block updates from one cache to another . The number of lms server processes running is       determined by gcs_server_processes . Default value for gcs_server_processes is 2 and can be increased to 32 .
LMDn  : manages requests for global enqueues . (across node )
LCK0 :handle resources not requiring Cache Fusion like library cache etc. (same node)
LMON ( global enqueue service monitor  for shared locks ) : also used by css . (across node )
DIAG : collect diagnostic info

- LMS—Global Cache Service Process
- LMD—Global Enqueue Service Daemon
- LMON—Global Enqueue Service Monitor
- LCK0—Instance Enqueue Process


GSD 9i is not compatible with 10g


RMSn
This process is called as Oracle RAC Management Service/Process. These processes perform manageability tasks for Oracle RAC. Tasks include creation of resources related Oracle RAC when new instances are added to the cluster.

RSMN
This process is called as Remote Slave Monitor. This process manages background slave process creation and communication on remote instances. This is a background slave process. This process performs tasks on behalf of a coordinating process running in another instance.


rbal : corordinate with asm instance
asmb :

GTX0-j—Global Transaction Process


2 main background process are RBAL and ASMB. RBAL process is used to make global calls to disk in diskgroup . ASMB process communicates with CSS daemon on node and receives file extend map information from ASM instance . ASMB is also responsible for providing I/O stats to ASM instance . asmb process is first started when files are first accessed .


ASM BACKGROUND PROCESSES :

DIA0
ASMB : when asmcmd invoked
RBAL : rebalance activity
ARBn
ACFS
Bnnn
CJQ0
CKPT
CPnn
GMON


asm instance has 3 background processes . RBAL , gmon and ARBn .RBAL process decides when rebalancing needs to be done and estimates how much time will it take .  RBAL process then invokes ARBn process to do actuall work . The number of ARBn processes generated depends upon asm_power_limit parameter set . Gmon is responsible for group monitoring .



Database backgroung process :
ACMS
ASnn
BMRn
DIA0
DMON
DWnn


>>>>>>>>>>>>>>>>>>> 9i
pmon
smon
arch
lgwr
DBWn
mrp
ckpt


>>>>>>>>>>>>>> 10g
mmon
mmnl
mman
RVWR
CTWR
M000


>>>>>>>>>>>>>>  11G Background Process=============
 
ABMR : automatic block media recovery
dbrm : DB resource manager
dia0 : Diagnosability process
fbda : Flashback data archiver process
vktm : Virtual Timekeeper
w000 : Space Management Co-ordination process
smc0 : Space Manager process



>>>>>>>>>>

MMAN :
Memory Manager (MMAN) coordinates the sizing of different memory components within SGA.
MMAN keeps a track of sizes of components and allocates/de-allocates memory based on their usage.
This process is used only when you enable Automatic Shared Memory Management


MMON :
The memory monitor (MMON) process was introduced in 10g is responsible for gathering statistics for Automatic Workload Repository.
This helps Oracle doing automatic problem detection and self tuning.

SMON :
System Monitor process performs recovery after instance failure and monitors temporary segments and extents.
SMON can also perform instance recovery for other failed RAC instances.

PMON :
Process Monitor recovers failed user process resources.  PMON performs cleanup of user process resources such as releasing locks.

DBWR :
Database Writer or Dirty Buffer Writer are responsible for writing dirty buffers from the database block cache to the database data files. Generally, DBWR only writes blocks back to the data files on commit, or when the cache is full and space has to be made for more blocks. The DBWR processes in RAC must be coordinated through the locking and global cache processes to ensure efficient processing is accomplished.  Oracle 11g allows for a maximum of 20 DBWR processes.


LGWR :
Log Writer process is responsible for writing the log buffers out to the redo logs. In RAC, each RAC instance has its own LGWR process that maintains that instance’s thread of redo logs.  Redo log entries are written sequentially.


ARCH : (Optional).
When running in ARCHIVELOG mode, the archive process writes filled redo logs to the archive log location(s).  The archive log files are critical for RAC and non-RAC database recovery.

CKPT :
A database checkpoint is a method where the state of a database is saved.  The checkpoint process writes checkpoint information to control files and data file headers.  Remember that the checkpoint process is the manager of the database checkpoint; the actual writing of blocks to disk is done by DBWR