崩溃恢复（crashrecovery）与AUTORESTART参数-Mysql Tutorial-php.cn

关于这个参数设置的影响，在生产系统中经历过两次：第一次是有套不太重要的系统安装在虚拟机，这套系统所有应用（DB2 WAS IHS）都配置到/etc/rc.local中，每次启动机器会自动拉起应用，然后有次虚拟机宕机，重启后检查了各个应用进程都正常启动，但是前台页

关于这个参数设置的影响，在生产系统中经历过两次：
第一次是有套不太重要的系统安装在虚拟机，这套系统所有应用（DB2 WAS IHS）都配置到/etc/rc.local中，每次启动机器会自动拉起应用，然后有次虚拟机宕机，重启后检查了各个应用进程都正常启动，但是前台页面访问异常无法访问，然后到后台手动连接数据库报：
SQL1015N The database is in an inconsistent state. SQLSTATE=55025
根据SQL1015N提示：需要执行RESTART DATABASE DBNAME命令，执行后然后数据库可以正常连接

第二次是一套HA服务器的主机电源故障发生系统切换，切换到备机后，检查应用都正常被拉起，但是前台无法访问，和第一次是相同的问题，AUTORESTART参数被设置了OFF

这个参数解释如下：
如果DB2数据库遭受断电或者异常关闭，数据库没有干净的关闭，那么数据库在启动的时候将会进行crash recovery. 但是如果数据库参数AUTORESTART设置为OFF的话，在启动数据库后DB2不会进行CRASH RECOVERY。关于crash recovery，在db2diag.log日志会有相关体现

下面重现这一场景：

/* 1 设置AUTORESTART为OFF */ [db2inst1@limt ~]$ db2 UPDATE DATABASE CONFIGURATION for limtdb USING AUTORESTART OFF IMMEDIATE DB20000I The UPDATE DATABASE CONFIGURATION command completed successfully. [db2inst1@limt ~]$ db2 get db cfg for limtdb|grep -i AUTORESTART Auto restart enabled (AUTORESTART) = OFF [db2inst1@limt yunwei]$ db2 connect to limtdb Database Connection Information Database server = DB2/LINUXX8664 10.1.0 SQL authorization ID = DB2INST1 Local database alias = LIMTDB /* 2 插入一条数据但不提交，为了数据库处于不一致性 */ [db2inst1@limt yunwei]$ db2 +c "insert into A values(15485,'asdas','asdas')" DB20000I The SQL command completed successfully. [db2inst1@limt yunwei]$ /* 3 kill数据库，模拟异常宕机情况 */ [db2inst1@limt yunwei]$ ps -ef|grep db2sys db2inst1 5287 5285 1 08:07 pts/1 00:00:04 db2sysc 0 db2inst1 5827 3612 0 08:12 pts/1 00:00:00 grep db2sys [db2inst1@limt yunwei]$ kill -9 5287 /* 4 启动数据库，此时数据库没有进行崩溃恢复，因为AUTORESTART为OFF */ [db2inst1@limt yunwei]$ [db2inst1@limt yunwei]$ db2start 12/19/2014 08:13:04 0 0 SQL1063N DB2START processing was successful. SQL1063N DB2START processing was successful. [db2inst1@limt yunwei]$ [db2inst1@limt yunwei]$ /* 5 此处报错是因为刚才的db2bp进程没有terminate */ [db2inst1@limt yunwei]$ db2 connect to limtdb SQL0752N Connecting to a database is not permitted within a logical unit of work when the CONNECT type 1 setting is in use. SQLSTATE=0A001 [db2inst1@limt yunwei]$ db2 terminate DB20000I The TERMINATE command completed successfully. /* 6 再次启动时候报数据库不一致 */ [db2inst1@limt yunwei]$ db2 connect to limtdb SQL1015N The database is in an inconsistent state. SQLSTATE=55025 /* 7 db2 ? SQL1015N 有一条建议： using the RESTART DATABASE command*/ [db2inst1@limt yunwei]$ db2 restart database limtdb DB20000I The RESTART DATABASE command completed successfully. /* 8 数据库可以正常连接*/ [db2inst1@limt yunwei]$ db2 connect to limtdb Database Connection Information Database server = DB2/LINUXX8664 10.1.0 SQL authorization ID = DB2INST1 Local database alias = LIMTDB /* 9 以下是设置AUTORESTART为ON情况下，数据库宕机重启(不需要执行RESTART DATABASE) */ [db2inst1@limt yunwei]$ [db2inst1@limt yunwei]$ db2 UPDATE DATABASE CONFIGURATION for limtdb USING AUTORESTART ON IMMEDIATE DB20000I The UPDATE DATABASE CONFIGURATION command completed successfully. [db2inst1@limt yunwei]$ [db2inst1@limt yunwei]$ db2 get db cfg for limtdb|grep -i AUTORESTART Auto restart enabled (AUTORESTART) = ON [db2inst1@limt yunwei]$ [db2inst1@limt yunwei]$ [db2inst1@limt yunwei]$ db2 +c "insert into A values(15485,'asdas','asdas')" DB20000I The SQL command completed successfully. [db2inst1@limt yunwei]$ ps -ef|grep db2sys db2inst1 5870 5868 1 08:13 pts/1 00:00:03 db2sysc 0 db2inst1 6122 3612 0 08:16 pts/1 00:00:00 grep db2sys [db2inst1@limt yunwei]$ kill -9 5870 [db2inst1@limt yunwei]$ db2start 12/19/2014 08:16:35 0 0 SQL1063N DB2START processing was successful. SQL1063N DB2START processing was successful. [db2inst1@limt yunwei]$ db2 connect to limtdb SQL0752N Connecting to a database is not permitted within a logical unit of work when the CONNECT type 1 setting is in use. [db2inst1@limt yunwei]$ db2 terminate DB20000I The TERMINATE command completed successfully. [db2inst1@limt yunwei]$ db2 connect to limtdb Database Connection Information Database server = DB2/LINUXX8664 10.1.0 SQL authorization ID = DB2INST1 Local database alias = LIMTDB

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