为何而心跳-Oracle Heartbeat研究

在Oracle中有一个事件叫Heartbeat，这个词在很多地方被提及，并且有着不同的含义(比如RAC中)，我们这里要讨论的是CKPT的Heartbeat机制。

Oracle通过CKPT进程每3秒将Heartbeat写入控制文件，以减少故障时的恢复时间(这个我们后面再详细阐述)。

我们可以通过如下方法验证这个过程。

1.首先在系统级启用10046时间跟踪

并重新启动数据库使之生效

[oracle@jumper oracle]$ sqlplus "/ as sysdba"

SQL*Plus: Release 9.2.0.4.0 - Production on Thu Jan 19 09:24:04 2006

Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production

SQL> alter system set event='10046 trace name context forever,level 12' scope=spfile;

System altered.

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL> startup
ORACLE instance started.

Total System Global Area  114365800 bytes
Fixed Size                   451944 bytes
Variable Size              50331648 bytes
Database Buffers           62914560 bytes
Redo Buffers                 667648 bytes
Database mounted.
Database opened.
SQL> exit
Disconnected from Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production