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checkpoint

原创 Linux操作系统 作者:psufnxk2000 时间:2013-10-16 22:50:04 0 删除 编辑
 Oracle Database uses the following types of checkpoints:

CKPT写检查点到数据文件头和控制文件 。检查点发生有很多情况,例如,数据库使用下面类型的检查点

Thread checkpoints 线程检查点  (可以认为是数据库检查点)

The database writes to disk all buffers modified by redo in a specific thread before a certain target. The set of thread checkpoints on all instances in a database is a database checkpoint. Thread checkpoints occur in the following situations: 线程检查点 发生在下面的情况

Consistent database shutdown 一致性关闭数据库

ALTER SYSTEM CHECKPOINT statement   alter ssytem checkpoint语句

Online redo log switch 在线日志文件切换

ALTER DATABASE BEGIN BACKUP statement   alter database begin backup语句

Tablespace and data file checkpoints  表空间和数据文件检查 点

The database writes to disk all buffers modified by redo before a specific target. A tablespace checkpoint is a set of data file checkpoints, one for each data file in the tablespace. These checkpoints occur in a variety of situations, including making a tablespace read-only or taking it offline normal, shrinking a data file, or executing ALTER TABLESPACE BEGIN BACKUP.

数据库写到磁盘所有的buffer修改。 表空间检查点是表空间中所有数据文件的检查点。这些检查点在 使表空间离线,收缩数据文件,alter tablespace begin backup语句时发生

Incremental checkpoints  增量检查点

An incremental checkpoint is a type of thread checkpoint partly intended to avoid writing large numbers of blocks at online redo log switches. DBWn checks at least every three seconds to determine whether it has work to do. When DBWn writes dirty buffers, it advances the checkpoint position, causing CKPT to write the checkpoint position to the control file, but not to the data file headers.

增量检查点是线程检查点的一种类型,避免在日志切换时要写大量的块。dbwn每三秒检查一次是否工作。当dbwn写脏缓存时推进检查点的位置。产生了ckpt写到控制文件,但不写数据文件头

Other types of checkpoints include instance and media recovery checkpoints and checkpoints when schema objects are dropped or truncated.

别的类型的检查点还有 实例和介质恢复的检查点,当对象删除或truncate的检查点

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/25099483/viewspace-774509/,如需转载,请注明出处,否则将追究法律责任。

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