在12c下，RAC集群分为标准集群和flex集群，可如下方式查看
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$ crsctl get cluster mode status
- Cluster is running in "standard" mode
1. GNS准备
GNS也需要配置DNS，可以用DHCP动态分配IP，也可以在DNS中静态分配。这里用DNS静态分配。
如果一开始未配置GNS，会有如下显示
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$ srvctl status gns
- PRKF-1117 : GNS server is not configured in this cluster.
见：为RAC 11g配置DNS，NTP，DHCP服务
2）DNS配置
DNS中保留SCAN IP的解析，添加GNS VIP条目
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vi demo.com.db
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……
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gns.demo.com IN A 192.168.6.24
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vi 192.168.6.db
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……
- 24 PTR gns.demo.com.
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$ cat /etc/resolv.conf
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search demo.com grid.demo.com
- nameserver 192.168.6.23
2. 添加GNS资源
以root用户执行GNS添加
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- # /u01/app/12.1.0/grid/bin/srvctl add gns -vip 192.168.6.24 -domain grid.demo.com
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- # /u01/app/12.1.0/grid/bin/srvctl start gns
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$ srvctl status gns
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GNS is running on node node1.
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GNS is enabled on node node1.
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$ srvctl status gns -node node2
GNS is not running on node node2.
GNS is enabled on node node2.
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$ crsctl status res -t
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……
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ora.gns
- 1 ONLINE ONLINE node1 STABLE
http://blog.itpub.net/22621861/viewspace-2112288/
4.将标准集群转换为Flex集群
以root用户运行
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# /u01/app/12.1.0/grid/bin/crsctl set cluster mode flex
- CRS-4933: Cluster mode set to "flex"; restart Oracle High Availability Services on all nodes for cluster to run in "flex" mode.
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#关闭RAC
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/u01/app/12.1.0/grid/bin/crsctl stop crs
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#启动RAC
- /u01/app/12.1.0/grid/bin/crsctl start crs -wait
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$ crsctl get cluster mode status
- Cluster is running in "flex" mode
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$ crsctl get node role status -all
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Node 'node1' active role is 'hub'
- Node 'node2' active role is 'hub'