Under the Oracleapproach to data change, when you issue an instruction to change an item ofdata, Oracle doesn’t just go to a data file (or the in-memory copy if the itemhappens to be buffered), find the item, and change it. Instead, Oracle worksthrough four critical steps to make t...
Redo Logs分为在线重做日志和归档重做日志 online Redo log files--在线重做日志,又称联机重做日志,指Oracle以SQL脚本的形式实时记录数据库的数据更新,换句话说,实时保存已执行的SQL脚本到在线日志文件中(按特定的格式)。 Archive Redo log files--归档重做日志,简称归档日志,指当条件满足时,Oracle将在线重做日志以文...
Oracle redo logs consists of two or more pre-allocated files which record all changes made to the database. Every instance of Oracle database has its own redo logs which protects the database in case of instance failure. The database require minimum of two redo log files to guarantee that ...
Oracle doesn’t just go to a data file (or the in-memory copy if the itemhappens to be buffered), find the item, and change it. Instead, Oracle worksthrough four critical steps to make the change happen. Stripped to the bareminimum of detail, these are ...
How Oracle Database Writes to the Redo Log 1.在非归档模式下 一个写满日志的日志文件要被reuse,必须等待这个写满日志的日志文件的重做日志被写入磁盘的数据文件中 2.在归档模式下 一个写满日志的日志文件要被reuse,必须等待这个写满日志的日志文件的重做日志被写入磁盘的数据文件中,并且这个写满日志的日志文件...
Oracle的REDO和UNDO 在这里会介绍UNDO,REDO是如何产生的,对TRANSACTIONS的影响,以及他们之间如何协同工作的。 什么是REDO REDO记录transaction logs,分为online和archived。以恢复为目的。 比如,机器停电,那么在重起之后需要online redo logs去恢复系统到失败点。 比如,磁盘坏了,需要用archived redo logs和online redo ...
以下是原厂手册中的说明：In the context of recovery, the undo information is used to undo the effects of uncommitted transactions, once all the datafile changes from the redo logs have been applied to the datafiles. The database is actually opened before the undo is applied.You ...
Guidelines for Sizing Redo Logs for an Oracle DatabaseThis topic is part of Configuring an Oracle Database for Siebel Applications. If redo logs are too small, frequent log switches occur, creating resource-intensive Oracle Database check-pointing in which all dirty buffers are flushed. A range...
innodb_undo_logs:指定回滚段的数量,默认为128个,也就是之前的innodb_rollback_segments。 innodb_undo_tablespaces:指定Undo-log分成几个文件来存储,必须开启innodb_undo_directory参数。 innodb_undo_log_truncate:是否开启Undo-log的在线压缩功能,即日志文件超过大小一半时自动压缩,默认OFF关闭。
因此可以基于binlog做到类似于oracle的闪回功能,其实都是依赖于binlog中的日志记录。 什么时候产生: 事务提交的时候,一次性将事务中的sql语句(一个事物可能对应多个sql语句)按照一定的格式记录到binlog中。 这里与redo log很明显的差异就是redo log并不一定是在事务提交的时候刷新到磁盘,redo log是在事务开始之后就...