Oracle architecture and backup (11) bcakground-process

1. What are background processes? Oracle background processes include DatabaseWriter (DBWR), LogWriter (LGWR), SystemMonitor (SMON), and ProcessMonitor, PMON), CheckpointProcess (CKPT), archiving process, service process, user process. Data Writing Process

1. background processes Oracle background processes include DatabaseWriter (DBWR), Log Writer (LGWR), and System Monitor (SMON) process Monitor (PMON), Checkpoint Process (CKPT), archiving Process, service Process, and user Process. Data Writing Process

1. What are background processes?

Oracle background processes include DatabaseWriter, DBWR, Log Writer, LGWR, System Monitor, and SMON) checkpoint Process (CKPT), archiving Process, service Process, and user Process.

Data Writing Process: responsible for writing changed data from the database buffer cache to the data file

Log writing process: writes changes in the redo log buffer to online redo log files.

System Monitoring: Checks Database Consistency and starts database recovery when the database is opened if necessary.

Process Monitoring: clears resources when an Oracle process fails.

Checkpoint Process: updates the database status information in control files and data files whenever changes in the buffer cache are permanently recorded in the database. The process changes the title of all data files at the check point to indicate the checkpoint. Generally, this task is executed by LGWR. However, if the checkpoint significantly reduces system performance, the CKPT process can run to separate the work of the checkpoint originally executed by the LGWR process, which is implemented by the CKPT process. For many applications, the CKPT process is unnecessary. CKPT runs only when the database has many data files and the LGWR significantly reduces the performance at the check point. The CKPT process does not write blocks to the disk. This task is completed by DBWR. The CHECKPOINT_PROCESS parameter in the init. ora file controls the Enable or enable CKPT process. The default value is FALSE.

Archiving process: backs up or archives a full log group during each log switch.

Service Process: User process service.

User process: On the client, the user is responsible for passing the user's SQL statement to the service process and retrieving the query data from the server segment.

To maximizeperformance and accommodate extends users, a multiprocess Oracle Database systemusesBackground processes. Background processes extends lidate functions that wowould otherwise be handled bymultiple database programs running for each user process. Background extends perform I/O and monitor other Oracle Database processes toprovide increased parallelism for better performance and reliability.

Example 2

SQL> exitDisconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0-ProductionWith the Partitioning, OLAP and Data Mining options [oracle @ localhost desktop] $ ps-ef | grep ora_oracle 2638 1 0 16:43? 00:00:00 ora_pmon_orcloracle 2640 1 0? 00:00:00 ora_psp0_orcloracle 2642 1 0? 00:00:00 ora_mman_orcloracle 2644 1 0? 00:00:00 ora_dbw0_orcloracle 2646 1 0? 00:00:00 ora_lgwr_orcloracle 2648 1 0? 00:00:00 ora_ckpt_orcloracle 2650 1 0? 00:00:00 ora_smon_orcloracle 2652 1 0? 00:00:00 ora_reco_orcloracle 2654 1 0? 00:00:00 ora_cjq0_orcloracle 2656 1 0? 00:00:00 ora_mmon_orcloracle 2658 1 0? 00:00:00 ora_mmnl_orcloracle 2660 1 0? 00:00:00 ora_d000_orcloracle 2662 1 0? 00:00:00 ora_s000_orcloracle 2666 1 0? 00:00:00 ora_qmnc_orcloracle 2683 1 0? 00:00:00 ora_q000_orcloracle 2685 1 0? 00:00:00 ora_q001_orcloracle 2720 1 0? 00:00:00 ora_j000_orcloracle 2723 2597 0 00:00:00 pts/0 grep ora _ [oracle @ localhost desktop] $ ps-ef | grep ora _ | egrep "pmon | smon | dbw0 | lgw | ckpt" oracle 2638 1 0? 00:00:00 ora_pmon_orcloracle 2644 1 0? 00:00:00 ora_dbw0_orcloracle 2646 1 0? 00:00:00 ora_lgwr_orcloracle 2648 1 0? 00:00:00 ora_ckpt_orcloracle 2650 1 0? 00:00:00 ora_smon_orclSQL> desc v $ bgprocess; Name Null? Type ---------------------------------------------- -------------------------- paddr raw (4) PSERIAL # number name VARCHAR2 (5) DESCRIPTION VARCHAR2 (64) error numberselect * FROM v $ bgprocess; SQL> SELECT * FROM V $ bgprocess WHERE paddr <> '00' 2; paddr pserial # NAME -------- ---------- description error cause ---------- 52A16830 1 PMONprocess cleanup ########### 52A16DE4 1 PSP0process spawner 0 ########## 52A17398 1 MMANMemory Manager ########## paddr pserial # NAME -------- ---------- ----- description error Response ---------- 52A1794C 1 DBW0db writer process 0 ######### #52A17F00 1 LGWRRedo etc. ######### 52A184B4 1 CKPTcheckpoint ########## paddr pserial # NAME -------- ---------- ----- description error details ---------- 52A18A68 1 SMONSystem Monitor Process # ######## 52A1901C 1 RECOdistributed recovery ########### 52A195D0 1 CJQ0Job Queue Coordinator ######### PADDR PSERIAL # NAME -------- ---------- ----- description error cause ---------- 52A1B808 1 QMNCAQ Coordinator ########## 52A19B84 1 MMONManageability Monitor Process ######### 52A1A138 1 MMNLManageability Monitor Process 2 ########## 12 rows selected. SQL> col description for a10; SQL> col error clear; SQL> SELECT name FROM v $ bgprocess WHERE paddr <> '00'; NAME-----PMONPSP0MMANDBW0LGWRCKPTSMONRECOCJQ0QMNCMMONNAME-----MMNL12 rows selected. SQL> set pagesize 99; SQL> SELECT name FROM v $ bgprocess WHERE paddr <> '00'; NAME-----PMONPSP0MMANDBW0LGWRCKPTSMONRECOCJQ0QMNCMMONMMNL12 rows selected.

Summary

1. background processes are those that run with the database. The following processes are very important: dbwr dbwn pmon smon ckpt.

2. Run the ps command in Linux to view the background process information.

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