一 什么是smon进程
the systemmonitor performs recovery when a failed instance starts up again. in an oraclereal 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.
作用：
实例恢复
前滚所有重做日志中的改变
打开数据库为了用户能访问
回滚没有提交的事务
接合自由的空间（coalesce every three secons）
释放临时表空间（deal located）
二 操作示例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.--出现此问题：关闭数据库，然后重启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.
三 总结
1. smon：系统监控进程，静态注册监听
2.smon作用：实例恢复、接合自由的空间（coalesceevery three secons）、
释放临时表空间（deal located）
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