Oracle architecture and backup (12) bg-smon

1. What is the SMON process Thesystemmonitorperformsrecoverywhenafailedinstancestartsupagain. InanOracleRealApplicationClustersdatabase, namely

One is The SMON process the systemmonitor performs recovery when a failed instance starts up again. In an internal lereal Application Clusters database, The SMON process of one instance canperform instance recovery for other instances that have faile

1. What is a SMON process?

The systemmonitor performs recovery when a failed instance starts up again. in an internal lereal Application Clusters database, the SMON process of one instance canperform instance recovery for other instances that have failed. SMON alsocleans up temporary segments that are no longer in use and recovers deadtransactions skipped during system failure and instance recovery because offile-read or offline errors. these transactions are eventually recovered bySMON when the tablespace or file is brought back online.

Purpose:

Instance recovery

Roll back changes in all redo logs

Open the database for user access

Roll back uncommitted transactions

Join free space (Coalesce every three secons)

Release temporary tablespace (Deal Located)

Example 2

SQL> startup force; ORACLE instance started. total System Global Area 838860800 bytesFixed Size 1222192 bytesVariable Size 775948752 bytesDatabase Buffers 58720256 bytesRedo Buffers 2969600 bytesDatabase mounted. database opened. SQL> startup force mount; ORACLE instance started. total System Global Area 838860800 bytesFixed Size 1222192 bytesVariable Size 775948752 bytesDatabase Buffers 58720256 bytesRedo Buffers 2969600 bytesDatabase mounted. -- this problem occurs: Shut down the database, then restart SQL> alter database archivelog; alter database archivelog * ERROR at line 1: ORA-00265: instance recovery required, cannot set ARCHIVELOG modeSQL> shutdown immediate; ORA-01109: database not openDatabase dismounted. ORACLE instance shut down. SQL> startup; ORACLE instance started. total System Global Area 838860800 bytesFixed Size 1222192 bytesVariable Size 775948752 bytesDatabase Buffers 58720256 bytesRedo Buffers 2969600 bytesDatabase mounted. database opened. SQL> shutdown mount, SP2-0717: illegal SHUTDOWN optionSQL> shutdown immediate; Database closed. database dismounted. ORACLE instance shut down. SQL> startup mount; ORACLE instance started. total System Global Area 838860800 bytesFixed Size 1222192 bytesVariable Size 775948752 bytesDatabase Buffers 58720256 bytesRedo Buffers 2969600 bytesDatabase mounted. SQL> alter database noarchivelog; Database altered. SQL> alter database open; Database altered.

Summary

1. SMON: system monitoring process, static registration listening

2. Role of SMON: instance recovery, free join space (Coalesceevery three secons ),

Release temporary tablespace (Deal Located)

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