Sep 13, 2006

Oracle Background Processes, incl. 10gR2


--New in 10gR2


PSP0 (new in 10gR2) - Process SPawner - to create and manage other Oracle processes.
NOTE: There is no documentation currently in the Oracle Documentation set on this process.

LNS1(new in 10gR2) - a network server process used in a Data Guard (primary) database.

Further explaination From "What's New in Oracle Data Guard?" in the Oracle® Data Guard Concepts and Administration 10g Release 2 (10.2)

"During asynchronous redo transmission, the network server (LNSn) process transmits redo data out of the online redo log
files on the primary database and no longer interacts directly with the log writer process. This change in behavior allows the log writer (LGWR) process to write redo data to the current online redo log file and continue processing the next request without waiting for inter-process communication or network I/O to complete."


--New in 10gR1


MMAN - Memory MANager - it serves as SGA Memory Broker and coordinates the sizing of the memory components, which keeps track of the sizes of the components and pending resize operations. Used by Automatic Shared Memory Management feature.

RVWR -Recovery Writer - which is responsible for writing flashback logs which stores pre-image(s) of data blocks. It is used by Flashback database feature in 10g, which provides a way to quickly revert an entire Oracle database to the state it was in at a past point in time.
- This is different from traditional point in time recovery.
- One can use Flashback Database to back out changes that:
- Have resulted in logical data corruptions.
- Are a result of user error.
- This feature is not applicable for recovering the database in case of media
- The time required for flashbacking a database to a specific time in past is
DIRECTLY PROPORTIONAL to the number of changes made and not on the size
of the database.

Jnnn - Job queue processes which are spawned as needed by CJQ0 to complete scheduled jobs. This is not a new process.

CTWR - Change Tracking Writer (CTWR) which works with the new block changed tracking features in 10g for fast RMAN incremental backups.

MMNL - Memory Monitor Light process - which works with the Automatic Workload Repository new features (AWR) to write out full statistics buffers to disk as needed.

MMON - Memory MONitor (MMON) process - is associated with the Automatic Workload Repository new features used for automatic problem detection and self-tuning. MMON writes out the required statistics for AWR on a scheduled basis.

M000 - MMON background slave (m000) processes.

CJQn - Job Queue monitoring process - which is initiated with the job_queue_processes parameter. This is not new.

RBAL - It is the ASM related process that performs rebalancing of disk resources controlled by ASM.

ARBx - These processes are managed by the RBAL process and are used to do the actual rebalancing of ASM controlled disk resources. The number of ARBx processes invoked is directly influenced by the asm_power_limit parameter.

ASMB - is used to provide information to and from the Cluster Synchronization Services used by ASM to manage the disk resources. It is also used to update statistics and provide a heartbeat mechanism.

Changes about Queue Monitor Processes

The QMON processes are optional background processes for Oracle Streams Advanced Queueing (AQ) which monitor and maintain all the system and user owned AQ objects. These optional processes, like the job_queue processes, does not cause the instance to fail on process failure. They provide the mechanism for message expiration, retry, and delay, maintain queue statistics, remove processed messages from the queue table and maintain the dequeue IOT.

QMNx - Pre-10g QMON Architecture

The number of queue monitor processes is controlled via the dynamic initialisation parameter AQ_TM_PROCESSES. If this parameter is set to a non-zero value X, Oracle creates that number of QMNX processes starting from ora_qmn0_ (where is the identifier of the database) up to ora_qmnX_ ; if the parameter is not specified or is set to 0, then QMON processes are not created. There can be a maximum of 10 QMON processes running on a single instance. For example the parameter can be set in the init.ora as follows

aq_tm_processes=1 or set dynamically via alter system set aq_tm_processes=1;

QMNC & Qnnn - 10g QMON Architecture

Beginning with release 10.1, the architecture of the QMON processes has been changed to an automatically controlled coordinator slave architecture. The Queue Monitor Coordinator, ora_qmnc_, dynamically spawns slaves named, ora_qXXX_, depending on the system load up to a maximum of 10 in total.

For version 10.01.XX.XX onwards it is no longer necessary to set AQ_TM_PROCESSES when Oracle Streams AQ or Streams is used. However, if you do specify a value, then that value is taken into account. However, the number of qXXX processes can be different from what was specified by AQ_TM_PROCESSES. If AQ_TM_PROCESSES is not specified in versions 10.1 and above, QMNC only runs when you have AQ objects in your database.

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