崩溃恢复（crashrecovery）与AUTORESTART参数

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,&＃39;asdas&＃39;,&＃39;asdas&＃39;)"
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,&＃39;asdas&＃39;,&＃39;asdas&＃39;)"
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