Oracle backgroud Process
System Monitor
Process Name: SMON
Max Processes: 1
This process is responsible for instance recovery, if necessary, at instance startup. SMON also cleans up temporary segments that are no longer in use. It also coalesces contiguous free extents in dictionary managed tablespaces that have PCTINCREASE set to a non-zero value.
SMON wakes up about every 5 minutes to perform housekeeping activities. SMON must always be running for an instance.
Process Monitor
Process Name: PMON
Max Processes: 1
This process is responsible for performing recovery if a user process fails. It will rollback uncommitted transactions. PMON is also responsible for cleaning up the database buffer cache and freeing resources that were allocated to a process. PMON also registers information about the instance and dispatcher processes with network listener.
PMON wakes up every 3 seconds to perform housekeeping activities. PMON must always be running for an instance.
Checkpoint Process
Process Name: CKPT
Max processes: 1
Checkpoint process signals the synchronization of all database files with the checkpoint information. It ensures data consistency and faster database recovery in case of a crash.
CKPT ensures that all database changes present in the buffer cache at that point are written to the data files, the actual writing is done by the Database Writer process. The datafile headers and the control files are updated with the latest SCN (when the checkpoint occurred), this is done by the log writer process.
The CKPT process is invoked under the following conditions:
1. When a log switch is done.
2. When the time specified by the initialization parameter LOG_CHECKPOINT_TIMEOUT exists between the incremental checkpoint and the tail of the log; this is in seconds.
3. When the number of blocks specified by the initialization parameter LOG_CHECKPOINT_INTERVAL exists between the incremental checkpoint and the tail of the log; these are OS blocks.
4. The number of buffers specified by the initialization parameter FAST_START_IO_TARGET required to perform roll-forward is reached.
5. Oracle 9i onwards, the time specified by the initialization parameter FAST_START_MTTR_TARGET is reached; this is in seconds and specifies the time required for a crash recovery. The parameter FAST_START_MTTR_TARGET replaces LOG_CHECKPOINT_INTERVAL and FAST_START_IO_TARGET, but these parameters can still be used.
6. When the ALTER SYSTEM SWITCH LOGFILE command is issued.
7. When the ALTER SYSTEM CHECKPOINT command is issued.
Incremental Checkpoints initiate the writing of recovery information to datafile headers and controlfiles. Database writer is not signaled to perform buffer cache flushing activity here.
Lock Monitor
Process Name: LMON
processes: 1
Meant for Parallel server setups, Lock Monitor manages global locks and resources. It handles the redistribution of instance locks whenever instances are started or shutdown. Lock Monitor also recovers instance lock information prior to the instance recovery process. Lock Monitor co-ordinates with the Process Monitor to recover dead processes that hold instance locks.
Lock Manager Daemon
Process Name: LMDn
Max Processes: -
Meant for Parallel server setups, LMDn processes manage instance locks that are used to share resources between instances. LMDn processes also handle deadlock detection and remote lock requests
Lock processes
Process Name: LCK0 through LCK9
Max Processes: 10
Meant for Parallel server setups, the instance locks that are used to share resources between instances are held by the lock processes.
Block Server Process
Process Name: BSP0 through BSP9
Max processes: 10
Meant for Parallel server setups, Block server Processes have to do with providing a consistent read image of a buffer that is requested by a process of another instance, in certain circumstances.
Queue Monitor
Process Name: QMN0 through QMN9
Max Processes: 10
This is the advanced Queuing Time manager process. QMNn monitors the message queues. Failure of QMNn process will not cause the instance to fail.
Event Monitor
Process Name: EMN0/EMON
Max Processes: 1
This process is also related to Advanced Queuing, and is meant for allowing a publish/subscribe style of messaging between applications.
Recoverer
Process Name: RECO
Max processes: 1
Intended for distributed recovery. All in-doubt transactions are recovered by this process in the distributed database setup. RECO will connect to the remote database to resolve pending transactions.
Job Queue Processes
Process Name: J000 through J999 (Originally called SNPn processes)
Max Processes: 1000
Job queue processes carry out batch processing. All scheduled jobs are executed by these processes. The initialization parameter JOB_QUEUE_PROCESSES specifies the maximum job processes that can be run concurrently. If a job fails with some Oracle error, it is recorded in the alert file and a process trace file is generated. Failure of the Job queue process will not cause the instance to fail.
Dispatcher
Process Name: Dnnn
Max Processes: -
Intended for Shared server setups (MTS). Dispatcher processes listen to and receive requests from connected sessions and places them in the request queue for further processing. Dispatcher processes also pickup outgoing responses from the result queue and transmit them back to the clients. Dnnn are mediators between the client processes and the shared server processes. The maximum number of Dispatcher process can be specified using the initialization parameter MAX_DISPATCHERS.
Shared Server Processes
Process Name: Snnn
Max Processes: -
Intended for Shared server setups (MTS). These processes pickup requests from the call request queue, process them and then return the results to a result queue. The number of shared server processes to be created at instance startup can be specified using the initialization parameter SHARED_SERVERS.
Parallel Execution Slaves
Process Name: Pnnn
Max Processes: -
These processes are used for parallel processing. It can be used for parallel execution of SQL statements or recovery. The Maximum number of parallel processes that can be invoked is specified by the initialization parameter PARALLEL_MAX_SERVERS.
Trace Writer
Process Name: TRWR
Max Processes: 1
Trace writer writes trace files from an Oracle internal tracing facility.
Input/Output Slaves
Process Name: Innn
Max Processes: -
These processes are used to simulate asynchronous I/O on platforms that do not support it. The initialization parameter DBWR_IO_SLAVES is set for this purpose.
Wakeup Monitor Process
Process Name: WMON
Max Processes: -
This process was available in older versions of Oracle to alarm other processes that are suspended while waiting for an event to occur. This process is obsolete and has been removed.
Conclusion
With every release of Oracle, new background processes have been added and some existing ones modified. These processes are the key to the proper working of the database. Any issues related to background processes should be monitored and analyzed from the trace files generated and the alert log.[@more@]來自 “ ITPUB部落格 ” ,連結:http://blog.itpub.net/34596/viewspace-799587/,如需轉載,請註明出處,否則將追究法律責任。
相關文章
- Oracle backgroud Process【Blog 搬家】Oracle
- Samza文件翻譯 : Backgroud
- Oracle dedicated server process and shared server processOracleServer
- ORACLE SESSION 和 PROCESSOracleSession
- oracle中修改processOracle
- 在oracle裡把backugroupd process叫做oracle的deamon process咋樣Oracle
- run sql in the backgroud 後臺執行sqlSQL
- oracle process設定的注意事情Oracle
- oracle session和process的關係OracleSession
- oracle 817 ora_snp background processOracle
- oracle中session跟process的研究OracleSession
- Oracle Display the process of the procedure ( oracle pipe , dbms_output , prompt )Oracle
- 關於oracle裡的process總結Oracle
- 修改Oracle process 和 session 的方法--摘OracleSession
- Multiple-Process Oracle Systems (107)Oracle
- For oracle databases, if the top showing the oracle database, then oracle process is using the top cOracleDatabase
- oracle設定process需要注意的事情Oracle
- Tomcat + Oracle9i 超出最大processTomcatOracle
- AIX下nfs故障導致oracle process hangAINFSOracle
- ST's Ch02 修改Oracle User Process。Oracle
- Process Monitor Process (PMON) (121)
- 在Oracle中session和process的區別(轉)OracleSession
- oracle session和process的關係 .轉自CSDNOracleSession
- Oracle中的Connect、session、process的區別OracleSession
- oracle五大程式和server process介紹OracleServer
- Oracle 19c Concepts(15):Process ArchitectureOracle
- oracle一個process對應多個session測試OracleSession
- oracle LOGICAL standby ORA-04030: out of process memoryOracle
- (轉):學習Oracle動態效能表-(12)-V$PROCESSOracle
- oracle11g_background process後臺程式詳解Oracle
- (轉)Oracle動態效能檢視學習之v$processOracle
- 各平臺影響oracle Process數的引數(轉)Oracle
- Process Architecture
- ORACLE ORA-04030之 out of process memory when trying to allocateOracle
- Oracle記憶體結構(三)----Process Memory的詳細資訊Oracle記憶體
- 【Oracle九大效能檢視】之6.v$process檢視Oracle
- ORACLE資料庫使用者的process memory已耗盡Oracle資料庫
- Oracle OCP 1Z0 053 Q389(Recovery Writer Process)Oracle