Shulou(Shulou.com)06/02 Report--

Oracle 29845 1 0 Oct13? 00:00:44 ora_pmon_zxin

Oracle 29847 1 0 Oct13? 00:00:06 ora_psp0_zxin

Oracle 29849 1 0 Oct13? 00:00:09 ora_mman_zxin

Oracle 29851 1 0 Oct13? 00:00:18 ora_dbw0_zxin

Oracle 29853 1 0 Oct13? 00:00:23 ora_lgwr_zxin

Oracle 29855 1 0 Oct13? 00:01:22 ora_ckpt_zxin

Oracle 29857 1 0 Oct13? 00:00:09 ora_smon_zxin

Oracle 29859 1 0 Oct13? 00:00:00 ora_reco_zxin

Oracle 29861 1 0 Oct13? 00:01:01 ora_cjq0_zxin

Oracle 29863 1 0 Oct13? 00:00:30 ora_mmon_zxin

Oracle 29865 1 0 Oct13? 00:02:49 ora_mmnl_zxin

Oracle 29903 1 0 Oct13? 00:00:02 ora_qmnc_zxin

Oracle 31437 1 0 Oct13? 00:00:00 ora_q000_zxin

Oracle 31439 1 0 Oct13? 00:00:01 ora_q001_zxin

These are oracle background processes, and different processes have different tasks and correspond to different logs.

Naming rules:

Ora_ process name _ SID

Role of the process:

1) PMON: process Monitor (Process Monitor)

Monitor other processes (other background processes or user connection processes), restore or undo other processes if necessary, and release resources. For example, if we kill the oracle log writing process, PMON will monitor it in time and shutdown the database.

Another function is to register the instance with the Oracle TNS listener. When the instance starts, the PMON process asks for a recognized port address (unless specified directly) to see if a listener is up and running

2) SMON: system Monitor (System Monitor)

Clean up the temporary space and temporary period: clean up the temporary period in the temporary tablespace when the database is up, or the temporary period left over from some abnormal operations (half of the query is dropped by the user cancel, etc.)

Join free space and merge adjacent extent in tablespace

Perform instance recovery (Instance recovery): used for instance recovery after illegal database shutdown (apply Redo to roll forward, open database to provide access, roll back uncommitted data)

Offline (Offline) rollback segment, such as when modifying the undo tablespace of database

3) RECO: distributed database recovery (Distributed Database Recovery)

The RECO background process, which appears only in systems that allow distributed transactions, is a process used when there is a distributed option to automatically resolve failures in distributed transactions. A node RECO daemon automatically connects to the

In other databases, RECO automatically resolves all pending transactions. Any rows corresponding to pending transactions that have been processed are deleted from the suspended transaction table of each database. When the RECO background process of a database server attempts to establish communication with the same remote server

If the remote server is unavailable or the network connection cannot be established, RECO automatically connects again after a time interval.

4) CKPT: checkpoint process (Checkpoint Process)

The check point in charge of the oracle background. The so-called check point refers to flush the dirty data in the SGA to the data file. However, the CKPT process is only the header of the update data file to assist the process of actually establishing checkpoints (DBWn)

5) DBWn: database block writer (Database Block Writer)

The database block writer (DBWn) is the background process responsible for writing dirty blocks to disk.

6) LGWR: log writer (Log Writer)

The LGWR process is responsible for flushing the contents of the redo log buffer in SGA to disk. The job will be done if one of the following conditions is met:

The output is refreshed every 3 seconds.

When any transaction issues a commit

The redo log buffer 1max is 3 full, or it already contains 1 MB of buffered data

7) ARCn: archiving process (Archive Process)

ARCn usually copies the online redo log files to another location, provided that the database turns on archive mode.

8) cjq0 Job Queue Processes

Used to coordinate and manage job

(1) when configuring job_queue_processes, there will be Jnnn and CJQ0 processes

(2) there can be up to 1000 Jnnn processes.

(3) the Jnnn process is shared between job, but each Jnnn can only execute one job at the same time, and the memory it uses is in UGA.

(4) job is usually used to refresh materialization attempts.

(5) AQ is generally used in streams.

(6) CJQ0, as the coordinator of jnnn, controls the startup and shutdown of jnnn.

(7) the Jnnn process will only start when there is a job to deal with.

9) MMON,MMNL,Mnnn:Manageability Monitors

(1) for AWR (autmatic workload repository)

(2) MMNL is responsible for writing the statistics in SGA to the table.

(3) MMON monitors database performance and makes automatic tuning

(4) Mnnn belongs to the helper of MMON and helps with tuning.

10) QMNC and Qnnn Processes:Job Queue

(1) for AQ function

(2) Qnnn processes the coordinator of each message queue,QMNC as a Qnnn

(3) if aq_tm_processes is configured, the QMNC and Qnnn processes will be started. Regardless of whether there is a queue to deal with or not, Qnnn will start all of them.

11) Pnnn parallel process, which occurs when parallel processing is started (parallel query, parallel dml, parallel ddl, parallel rollback)

The startup sequence of the main background processes:

PMON started with pid=2, OS id=18279

PSP0 started with pid=3, OS id=18281

MMAN started with pid=4, OS id=18283

DBW0 started with pid=5, OS id=18285

DBW1 started with pid=6, OS id=18287

Log path of background process: $ORACLE_BASE/admin/zxin/bdump

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