Oracle12C支持兩種集群模式：Standard和Flex。
11G即是Standard的纸淮；Flex是12C的新特性。
當(dāng)將Standard修改為Flex時，出現(xiàn)如下問題：
# crsctl set cluster mode flex
CRS-4937: Unable to set the cluster mode.
查看官方文檔蒿往，發(fā)現(xiàn)需要配置GNS，Standard模式下不需要GNS湿弦，但是Flex模式是需要的瓤漏。
下面是官方文檔（加入翻譯）。
1. Run the following command to determine the current mode of the cluster:
確認(rèn)當(dāng)前集群模式：
$ crsctl get cluster mode status
2. Run the following command to ensure that the Grid Naming Service (GNS) is configured with a fixed VIP:
確認(rèn)GNS配置。
$ srvctl config gns
This procedure cannot succeed unless GNS is configured with a fixed VIP. If there is no GNS, then, as root, create one, as follows:
GNS需要配置flexed-VIP的蔬充，如果沒有配置蝶俱，需要使用root用戶創(chuàng)建一個。
# srvctl add gns -vip vip_name | ip_address
注意：要與集群公網(wǎng)在同一個網(wǎng)段饥漫。
Run the following command as root to start GNS:
啟動GNS榨呆。
# srvctl start gns
3. Use the Oracle Automatic Storage Management Configuration Assistant (ASMCA) to enable Oracle Flex ASM in the cluster before you change the cluster mode.
使用asmca將ASM存儲轉(zhuǎn)換為Flex ASM。
4. Run the following command as root to change the mode of the cluster to be an Oracle Flex Cluster:
以root身份庸队，配置集群模式為flex的积蜻。
# crsctl set cluster mode flex
5. Stop Oracle Clusterware by running the following command as root on each node in the cluster:
以root身份在一個節(jié)點(diǎn)執(zhí)行停止crs的命令。
# crsctl stop crs
6. Start Oracle Clusterware by running the following command as root on each node in the cluster:
以root身份在一個節(jié)點(diǎn)執(zhí)行啟動crs的命令彻消，即重啟集群竿拆。
# crsctl start crs -wait
Note: Use the -wait option to display progress and status messages.
