ARCH - (Optional)
Archive process writes filled redo logs to the
archive log location(s). In RAC, the various
ARCH processes can be utilized to ensure that
copies of the archived redo logs for each
instance are available to the other instances in
the RAC setup should they be needed for
CJQ - Job Queue
Process (CJQ) - Used for the job scheduler. The
job scheduler includes a main program (the
coordinator) and slave programs that the
coordinator executes. The parameter
job_queue_processes controls how many parallel
job scheduler jobs can be executed at one time.
CKPT - Checkpoint
process writes checkpoint information to control
files and data file headers.
CQJ0 - Job queue
controller process wakes up periodically and
checks the job log. If a job is due, it spawns
Jnnnn processes to handle jobs.
DBWR - Database
Writer or Dirty Buffer Writer process is
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
possible multiple DBWR processes in RAC must be
coordinated through the locking and global cache
processes to ensure efficient processing is
FMON - The database
communicates with the mapping libraries provided
by storage vendors through an external
non-Oracle Database process that is spawned by a
background process called FMON. FMON is
responsible for managing the mapping
information. When you specify the FILE_MAPPING
initialization parameter for mapping data files
to physical devices on a storage subsystem, then
the FMON process is spawned.
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.
LMON - Lock Manager
MMON - The Oracle
10g background process to collect statistics for
the Automatic Workload Repository (AWR).
MMNL - This process
performs frequent and lightweight
manageability-related tasks, such as session
history capture and metrics computation.
MMAN - is used for internal database tasks
that manage the automatic shared memory. MMAN
serves as the SGA Memory Broker and coordinates
the sizing of the memory components.
PMON - Process
Monitor process recovers failed process
resources. If MTS (also called Shared Server
Architecture) is being utilized, PMON monitors
and restarts any failed dispatcher or server
processes. In RAC, PMON's role as service
registration agent is particularly important.
Pnnn - (Optional)
Parallel Query Slaves are started and stopped as
needed to participate in parallel query
RBAL - This process
coordinates rebalance activity for disk groups
in an Automatic Storage Management instance.
SMON - System
Monitor process recovers after instance failure
and monitors temporary segments and extents.
SMON in a non-failed instance can also perform
failed instance recovery for other failed RAC
WMON - The "wakeup"
DMON - The Data
Guard Broker process.
SNP - The snapshot
MRP - Managed
recovery process - For Data Guard, the
background process that applies archived redo
log to the standby database.
ORBn - performs the
actual rebalance data extent movements in an
Automatic Storage Management instance. There can
be many of these at a time, called ORB0, ORB1,
and so forth.
OSMB - is present in a database instance
using an Automatic Storage Management disk
group. It communicates with the Automatic
Storage Management instance.
RFS - Remote File
Server process - In Data Guard, the remote file
server process on the standby database receives
archived redo logs from the primary database.
QMN - Queue Monitor Process (QMNn) - Used
to manage Oracle Streams Advanced Queuing.
background task for 10g and beyond.
Daemon - Monitors the health of the instance and
captures the data for instance process failures.
LCKx - This process
manages the global enqueue requests and the
cross-instance broadcast. Workload is
automatically shared and balanced when there are
multiple Global Cache Service Processes (LMSx).
LMON - The Global
Enqueue Service Monitor (LMON) monitors the
entire cluster to manage the global enqueues and
the resources. LMON manages instance and process
failures and the associated recovery for the
Global Cache Service (GCS) and Global Enqueue
Service (GES). In particular, LMON handles the
part of recovery associated with global
resources. LMON-provided services are also known
as cluster group services (CGS)
LMDx - The Global Enqueue Service Daemon
(LMD) is the lock agent process that manages
enqueue manager service requests for Global
Cache Service enqueues to control access to
global enqueues and resources. The LMD process
also handles deadlock detection and remote
enqueue requests. Remote resource requests are
the requests originating from another instance.
LMSx - The Global
Cache Service Processes (LMSx) are the processes
that handle remote Global Cache Service (GCS)
messages. Real Application Clusters software
provides for up to 10 Global Cache Service
Processes. The number of LMSx varies depending
on the amount of messaging traffic among nodes
in the cluster.
The LMSx handles the
acquisition interrupt and blocking interrupt
requests from the remote instances for Global
Cache Service resources. For cross-instance
consistent read requests, the LMSx will create a
consistent read version of the block and send it
to the requesting instance. The LMSx also
controls the flow of messages to remote
The LMSn processes handle
the blocking interrupts from the remote instance
for the Global Cache Service resources by:
Managing the resource
requests and cross-instance call operations
for the shared resources.
Building a list of
invalid lock elements and validating the
lock elements during recovery.
Handling the global
lock deadlock detection and Monitoring for
the lock conversion timeouts