Oracle RAC Flex ASM 特性测试

 
 在 Oracle 12c 之前，对于要使用 ASM 的数据库实例来说，所有节点上的 ASM 实例必须已处于运行状态，才能启动数据库实例。如果 ASM 实例未运行，则对应的数据库实例也无法启动。

 Oracle 12c 开始引入Oracle Flex ASM 的特性，解除了上述限制，它的一个主要特性是故障切换到集群中的其他节点。

下面，我们用19c RAC 环境，简单测试一下该特性：

1. 查看rac集群模式

[grid@rac1 ~]$ asmcmd showclustermode
ASM cluster : Flex mode enabled - Direct Storage Access  --> 默认已开启flex特性

2. 查看节点asm实例状态

[grid@rac1 ~]$ srvctl status asm -detail
ASM is running on rac2,rac1     -->asm在两个节点上都运行
ASM is enabled.
ASM instance +ASM1 is running on node rac1
Number of connected clients: 2
Client names: MESDB1:MESDB:mesdb-cluster rac1:_OCR:mesdb-cluster
ASM instance +ASM2 is running on node rac2
Number of connected clients: 2
Client names: MESDB2:MESDB:mesdb-cluster rac2:_OCR:mesdb-cluster

3. 查看数据库实例状态

[grid@rac1 ~]$ srvctl status database -d MESDB -detail
Instance MESDB1 is running on node rac1
Instance MESDB1 is connected to ASM instance +ASM1   -->此时节点1上的MESDB1实例连接的是+ASM1
Instance MESDB2 is running on node rac2
Instance MESDB2 is connected to ASM instance +ASM2   -->此时节点2上的MESDB2实例连接的是+ASM2

4. 强制关闭节点1上的asm实例

[grid@rac1 ~]$ ps -ef|grep pmon
oracle    2579     1  0 13:36 ?        00:00:00 ora_pmon_MESDB1
grid     11114  9590  0 13:45 pts/11   00:00:00 grep --color=auto pmon
grid     15935     1  0 May29 ?        00:00:05 asm_pmon_+ASM1


-- 方法1：
[grid@rac1 ~]$ kill -9 15935
[grid@rac1 ~]$ ps -ef|grep pmon
oracle    2579     1  0 13:36 ?        00:00:00 ora_pmon_MESDB1
grid     12175  9590  0 13:47 pts/11   00:00:00 grep --color=auto pmon

-- 方法2：
[root@rac1 ~]# srvctl stop asm -node rac1 -o abort -force
[root@rac1 ~]# ps -ef|grep pmon
oracle     3828      1  0 14:50 ?        00:00:00 ora_pmon_orcl1
root       7130 108701  0 14:56 pts/3    00:00:00 grep --color=auto pmon

5. 查看asm实例信息

[grid@rac1 ~]$ srvctl status asm
ASM is running on rac2  -->此时asm只在节点2上运行

[grid@rac2 ~]$ srvctl status asm -detail
ASM is running on rac2
ASM is enabled.
ASM instance +ASM2 is running on node rac2
Number of connected clients: 3
Client names: MESDB1:MESDB:mesdb-cluster MESDB2:MESDB:mesdb-cluster rac2:_OCR:mesdb-cluster



[grid@rac1 ~]$ srvctl status database -d MESDB -detail
Instance MESDB1 is running on node rac1
Instance MESDB1 is connected to ASM instance +ASM2   -->节点1上面的实例MESDB1，不在是连接+ASM1实例，自动切换到节点2上的asm实例+ASM2
Instance MESDB2 is running on node rac2
Instance MESDB2 is connected to ASM instance +ASM2   -->此时节点2上的MESDB2实例连接的仍然是+ASM2

6. 检查节点1上的数据库状态

[oracle@rac1 ~]$ sqlplus / as sysdba
SQL*Plus: Release 19.0.0.0.0 - Production on Tue May 30 13:52:37 2023
Version 19.19.0.0.0
Copyright (c) 1982, 2022, Oracle.  All rights reserved.
Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.19.0.0.0
SQL> set line222
SQL> select INST_ID,INSTANCE_NAME,STATUS from gv$instance;

   INST_ID INSTANCE_NAME                                    STATUS
---------- ------------------------------------------------ ------------------------------------
         1 MESDB1                                        OPEN
         2 MESDB2                                        OPEN

SQL> select INST_ID,name,open_mode from gv$database;

   INST_ID NAME                        OPEN_MODE
---------- --------------------------- ------------------------------------------------------------
         2 MESDB                    READ WRITE
         1 MESDB                    READ WRITE

结论：在节点1上数据库实例并未受到影响。 

7. 再次启动节点1的asm实例

[grid@rac1 ~]$ srvctl start asm -node rac1

[grid@rac1 ~]$ srvctl status asm -detail
ASM is running on rac2,rac1      --->asm实例又重新恢复，分别在2个节点上都运行
ASM is enabled.
ASM instance +ASM1 is running on node rac1
Number of connected clients: 2
Client names: MESDB1:MESDB:mesdb-cluster rac1:_OCR:mesdb-cluster
ASM instance +ASM2 is running on node rac2
Number of connected clients: 2
Client names: MESDB2:MESDB:mesdb-cluster rac2:_OCR:mesdb-cluster

8. 再次检查节点1上的数据库状态

--恢复到最初状态
[grid@rac1 ~]$ srvctl status database -d MESDB -detail
Instance MESDB1 is running on node rac1
Instance MESDB1 is connected to ASM instance +ASM1   -->此时节点1上的MESDB1实例连接的是+ASM1
Instance MESDB2 is running on node rac2
Instance MESDB2 is connected to ASM instance +ASM2   -->此时节点2上的MESDB2实例连接的是+ASM2

注释：关于停止ASM实例说明

--1) 如果采用方法1 kill 进程的方式，杀死asm实例，那么从集群状态可以看到，asm实例会自动重新启动
[grid@rac1 ~]$ crsctl stat res -t

ora.asm(ora.asmgroup)
      1        ONLINE  OFFLINE      rac1                Instance Shutdown,STARTING
      2        ONLINE  ONLINE       rac2                Started
ora.MESDB.db
      1        ONLINE  ONLINE       rac1                Open,HOME=/oracle/app/oracle/product/db/191900,STABLE
      2        ONLINE  ONLINE       rac2                Open,HOME=/oracle/app/oracle/product/db/191900,STABLE

--2)如果采用方法2，手动停止asm实例，asm 不会自动重新启动，需要手动启动
[grid@rac1 ~]$ crsctl stat res -t
ora.asm(ora.asmgroup)
      1        OFFLINE OFFLINE                        Instance Shutdown,STBLE
      2        ONLINE  ONLINE       rac2                Started,STABLE
ora.MESDB.db
      1        ONLINE  ONLINE       rac1                Open,HOME=/oracle/app/oracle/product/db/191900,STABLE
      2        ONLINE  ONLINE       rac2                Open,HOME=/oracle/app/oracle/product/db/191900,STABLE