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Redo Log Buffer (84)

原创 网络安全 作者:tsinglee 时间:2007-10-24 10:01:34 0 删除 编辑

The redo log buffer is a circular buffer in the SGA that holds information about

changes made to the database. This information is stored in redo entries. Redo entries

contain the information necessary to reconstruct, or redo, changes made to the

database by INSERT, UPDATE, DELETE, CREATE, ALTER, or DROP operations. Redo

entries are used for database recovery, if necessary.

Redo entries are copied by Oracle database processes from the user’s memory space to

the redo log buffer in the SGA. The redo entries take up continuous, sequential space

in the buffer. The background process LGWR writes the redo log buffer to the active

redo log file (or group of files) on disk.

The initialization parameter LOG_BUFFER determines the size (in bytes) of the redo log

buffer. In general, larger values reduce log file I/O, particularly if transactions are long

or numerous. The default setting is either 512 kilobytes (KB) or 128 KB times the

setting of the CPU_COUNT parameter, whichever is greater.

重做日志缓存区

Sga中一个循环缓存池保存对数据库改变的信息 ,这些信息以重做日志条目保存,

从用户内存区域拷贝到redo log buffer ,包括对insert , update等的重做信息 ,一般作为恢复用. Lgwr后台进程将redo log buffer中的信息写入到活动的日志组中。

大小由初始化参数log_buffer决定 ,一般来说 大的log_buffer可减少日志文件i/o [@more@]

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/10599713/viewspace-978358/,如需转载,请注明出处,否则将追究法律责任。

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