After RAC ONE NODE Failover and relocate ，instance_number 和 oracle_sid changes

        一套RAC ONE NODE 数据库由于asmb进程异常导致数据库failover，reolocate回原来的节点后，发现instance_number由1变为2，oracle_sid由xxx_1 变为xxx_2。由于数据库部署有ogg和其他需要指定sid的业务，所以请求官方解决sid 改变和asmb异常原因。

        提交sr后，官方给出如下文档，仔细对比后发现比较符合我的情况：

未failover之前是xxx_1(1节点），failover之后xxx_1(2节点）---与官方阐述是一致的；此后，我又relocate回到1节点，sid为xxx_2(1节点）。那么此时数据库认为1节点是主节点

relocate回1节点时是switchover也是符合文档中的解释的。

Instance Name changes during RAC One Node Failover/Switchover (文档 ID 1540629.1)转到底部

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In this Document

Purpose Scope Details

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APPLIES TO:

Oracle Database - Enterprise Edition - Version 11.2.0.1 to 11.2.0.3 [Release 11.2]
Oracle Database - Enterprise Edition - Version 12.1.0.2 to 12.1.0.2 [Release 12.1]
Information in this document applies to any platform.

PURPOSE

 Instance Name changes during RAC One NODE Failover / Switchover

SCOPE

 Instance Name changes

DETAILS

 
INSTANCE / NODE CRASH (FAILOVER):

     When the node goes down due to abnormal termination (  kill -9 or due to unknow reasons) Grid Infrastructure performs the following:

•  First cluster tries to restart the instance in same node. 
  
•  If it is unsuccessful then it will start the instance in other node.
•  If the instance name is orcl_1, when it failover to node 2 it will be still orcl_1.
            

INSTANCE RELOCATE MANUALLY(SWITCHOVER):

    When Manually switchover is performed for relocating orcl_1 from Node1 to Node 2 (Instance Relocation) Grid Infrastructure performs the following:

• It will first create pfile( init.ora) automatically in node 2.
• In node 2 it will use the new pfile and start instance with a new name, i.e. orcl_2, this is due to both instances are required to be up and running for active sessions on the original node to complete or time out.
  
• Post switchover, it uses new instance name i.e. orcl_2