CH02 日志.ppt

DB2 日志
开残仲弄刷犯层卢盾徊衅遮山鞠柞痹除瓶霞咙僧失跃翼沾可恫毗端舆工村CH02_日志CH02_日志
Logs record of transactions
If there is a crash, the Logs are used to playback/mitted transactions during recovery
Maximum log space allowed is 256GB
Logging is always on for regular tables in DB2
Possible to mark some tables or columns as NOT LOGGED
Possible to log USER temporary tables
There are two kinds of logging:
Circular logging (default)
Archive logging
Database Logging
胸盎迸却街疤野颅淀练垢猜虱爪叉镜翼揍革焦俭革员侵蝶榨陈乖呸弱勒地CH02_日志CH02_日志
2
Primary log files (LOGPRIMARY) used to record all changes; reused when changes mitted
Secondary log files (LOGSECOND) allocated when limit of primary log files reached
If both primary and secondary log limit is reached, an error code is the file system (LOGPATH) has insufficient space, a “log disk full error” will be raised
Crash and version recovery possible;
roll-forward recovery not possible
PRIMARY
SECONDARY
1
"n"
2
3
1
"n"
Circular Logging循环日志模式
逢去风越虏悦倍廖徘垣锌迪巧纷顾谚哇森圃科臂启榴慕脯尽嗓象色妈评常CH02_日志CH02_日志
3
循环日志模式
主日志文件(LOGPRIMARY)用来记录所有的变化,当该日志文件中所有的事务都提交完成后将被重用
辅助日志文件(LOGSECOND)是用来当主日志文件满了以后使用的
如果主日志文件和辅助日志文件都满了,就会收到一个错误“数据库事务日志已满”.
如果文件系统中LOGPATH目录没有空间了,就会收到一个磁盘满(log disk full error)错误
窒钩拦感将哗钩桓搔蛋哟捻饼衫苫疯掠武闽传居舶走怒俯陈耘昼着妒审姚CH02_日志CH02_日志
4
循环日志模式
循环日志模式是新创建数据库的缺省日志模式(将 logarchmeth1 和 logarchmeth2 数据库配置参数设置为 OFF。)
在循环日志模式下,只允许进行完全数据库脱机备份,不能进行表空间备份、联机备份、增量备份、差异备份等。
在循环日志模式下,可以使用崩溃恢复(Crash recovery)和版本恢复(Version recovery),但是不能使用前滚恢复(Roll-forward recovery)
砸肉林五栅下盗锌列嫡凤舀啤艇袜孟省固筹塑济莉熔溶丘赚尉莹视凳砚赘CH02_日志CH02_日志
5
Used for rollforward recovery. It is enabled with the LOGARCHMETH1 database configuration parameter
Logs are archived when no longer active (. not required for crash recovery). They are not deleted; they are kept online or offline
Rollforward recovery and online backup are possible
Archive Logging归档日志模式
12
13
14
15
16
Manual or
Value in LOGARCHMETH1
OFFLINE ARCHIVE - Archive moved from ACTIVE log subdirectory. (May also be on other media)
ONLINE ARCHIVE