保险系统维护
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AIX file systems by default are journaled, so every time a write operation is carried out, the system will first log all the changes that it is going to make in the log file,then it will carry out the update, and then it will compare the actual change to the logged changes. If the two are consistent the operation is considered successful and the log entry can then be discarded.
Note: ONLY inode changes are logged and not the changes for the data blocks. This is because it is far more important to be able to recover the structure of the file system, which is what the inodes will allow, rather than the individual data blocks.
AIX memory maps files in current use. Any writes to files are done first in memory and at a later stage are written out to disk when the sync system call runs - every minute.
当文件系统需要修改数据时，先将inode的变化记录在loglv中，待到内存中修改完数据 需要写回硬盘的时候，需要与loglv中inode变化 进行比较（同步），如果一致，即写回硬盘保存，如果不同，则不能写回。写回硬盘后，loglv中的该记录就可以丢弃。loglv可重用，即是循环使用。有点类似于非归档模式下oracle数据库redolog。
loglv只记录inode的变化，而不记录数据变化。收起
Note: ONLY inode changes are logged and not the changes for the data blocks. This is because it is far more important to be able to recover the structure of the file system, which is what the inodes will allow, rather than the individual data blocks.
AIX memory maps files in current use. Any writes to files are done first in memory and at a later stage are written out to disk when the sync system call runs - every minute.
当文件系统需要修改数据时，先将inode的变化记录在loglv中，待到内存中修改完数据 需要写回硬盘的时候，需要与loglv中inode变化 进行比较（同步），如果一致，即写回硬盘保存，如果不同，则不能写回。写回硬盘后，loglv中的该记录就可以丢弃。loglv可重用，即是循环使用。有点类似于非归档模式下oracle数据库redolog。
loglv只记录inode的变化，而不记录数据变化。收起
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