If Oracle allows multiple instances to mount the same database concurrently, then the

database administrator can use the CLUSTER_DATABASE initialization parameter to

make the database available to multiple instances. The default value of the CLUSTER_

DATABASE parameter is false. Versions of Oracle that do not support Real

Application Clusters only allow CLUSTER_DATABASE to be false.

If CLUSTER_DATABASE is false for the first instance that mounts a database, then

only that instance can mount the database. If CLUSTER_DATABASE is set to true on

the first instance, then other instances can mount the database if their CLUSTER_

DATABASE parameters are set to true. The number of instances that can mount the

database is subject to a predetermined maximum, which you can specify when

creating the database.

RAC系统中的数据库如何加载

1. 某些版本的 Oracle 允许多个实例同时装载同一个数据库,DBA 需要使用 CLUSTER_DATABASE

初始化参数来开启(设置为True , 某些版本只能为False)此项功能

2. 当第一个挂载数据库的实例的 CLUSTER_DATABASE 参数为 true 时,其它 CLUSTER_DATABASE

参数为 true 的实例也可以挂载同一个数据库