Using Oracle Flex ASM with single instance database

Oracle Flex ASM was introduced in 12c version. This is one of the best features introduced with new version in my opinion.

I won’t speak in detail about Flex ASM because you can find more information in documentation. In this post I will concentrate on how Flex ASM handles crash of ASM instance.

For this test I’ve created 2 node cluster - 12c Grid Infrastructure with Flex ASM enabled.

$ asmcmd showclustermode
ASM cluster : Flex mode enabled


$ srvctl config asm
ASM home: /u01/app/12.1.0/grid_1
Password file: +OCRVOTE/ASM/PASSWORD/pwdasm.256.853771307
ASM listener: LISTENER
ASM instance count: ALL
Cluster ASM listener: ASMNET1LSNR_ASM


$ srvctl status asm
ASM is running on cluster1,cluster2

Install single instance database on one of the nodes.

$ ./dbca -silent \
> -createDatabase \
> -templateName General_Purpose.dbc \
> -gdbName singl12 \
> -sid singl12 \
> -sysPassword oracle \
> -SystemPassword oracle \
> -emConfiguration none \
> -recoveryAreaDestination FRA \
> -storageType ASM \
> -asmSysPassword oracle \
> -diskGroupName DATA \
> -characterSet AL32UTF8 \
> -nationalCharacterSet AL16UTF16 \
> -totalMemory 768 \


Copying database files
1% complete
3% complete
10% complete
17% complete
24% complete
31% complete
35% complete
Creating and starting Oracle instance
37% complete
42% complete
47% complete
52% complete
53% complete
56% complete
58% complete
Registering database with Oracle Restart
64% complete
Completing Database Creation
68% complete
71% complete
75% complete
85% complete
96% complete
100% complete
Look at the log file "/u01/app/orcl12/cfgtoollogs/dbca/singl12/singl12.log" for further details.

Single instance database is registered to the OCR.

$ srvctl config database -d singl12
Database unique name: singl12
Database name: singl12
Oracle home: /u01/app/orcl12/product/12.1.0/dbhome_1
Oracle user: orcl12
Spfile: +DATA/singl12/spfilesingl12.ora
Password file:
Domain:
Start options: open
Stop options: immediate
Database role: PRIMARY
Management policy: AUTOMATIC
Server pools: singl12
Database instance: singl12
Disk Groups: DATA
Mount point paths:
Services:
Type: SINGLE  <<<<<-------
Database is administrator managed

V$ASM_CLIENT shows that my database is managed by the Oracle ASM instance.

SQL> select instance_name, db_name, status
  2  from v$asm_client
  3  where db_name='singl12';

INSTANCE_NAME        DB_NAME  STATUS
-------------------- -------- ------------
singl12              singl12  CONNECTED

Check that ASM instances are running on both nodes.

$ ./crsctl status resource ora.asm
NAME=ora.asm
TYPE=ora.asm.type
TARGET=ONLINE            , ONLINE
STATE=ONLINE on cluster2, ONLINE on cluster1

My database is running on cluster1 node.

$ srvctl status database -d singl12
Instance singl12 is running on node cluster1


SQL> select instance_name, host_name from v$instance;

INSTANCE_NAME   HOST_NAME
--------------- --------------------
singl12         cluster1.localdomain

Now I will simulate crash of ASM instance on cluster1 node where I have my database running.

# ps -ef|grep asm_pmon|grep -v grep
oracle    3072     1  0 10:12 ?        00:00:01 asm_pmon_+ASM1

# kill -9 3072

Without Flex ASM I would expect that crash of ASM instance would crash database instance also but with Flex ASM my database stays up and running.

Check alert log of database instance:

...
NOTE: ASMB registering with ASM instance as client 0x10005 (reg:2156157897)
NOTE: ASMB connected to ASM instance +ASM2 (Flex mode; client id 0x10005)
NOTE: ASMB rebuilding ASM server state
NOTE: ASMB rebuilt 1 (of 1) groups
NOTE: ASMB rebuilt 13 (of 13) allocated files
NOTE: fetching new locked extents from server
NOTE: 0 locks established; 0 pending writes sent to server
SUCCESS: ASMB reconnected & completed ASM server state

Check line - "NOTE: ASMB connected to ASM instance +ASM2 (Flex mode; client id 0x10005)"

As +ASM1 instance crashed ASMB connected to ASM instance +ASM2.


Check status:

# ./crsctl status resource ora.asm
NAME=ora.asm
TYPE=ora.asm.type
TARGET=ONLINE            , ONLINE
STATE=ONLINE on cluster2, INTERMEDIATE on cluster1


SQL> select instance_name, host_name from v$instance;

INSTANCE_NAME   HOST_NAME
--------------- --------------------
singl12         cluster1.localdomain

Oracle Clusterware restarted crashed ASM instance and both instances were up in a minute.

# ./crsctl status resource ora.asm
NAME=ora.asm
TYPE=ora.asm.type
TARGET=ONLINE            , ONLINE
STATE=ONLINE on cluster2, ONLINE on cluster1

Now to test crash ASM instance on second node.

SQL> select instance_name from v$instance;

INSTANCE_NAME
----------------
+ASM2

SQL> shutdown abort;
ASM instance shutdown

Excerpt from alertlog:

...
Fri Jul 25 12:44:33 2014
NOTE: ASMB registering with ASM instance as client 0x10005 (reg:4169355750)
NOTE: ASMB connected to ASM instance +ASM1 (Flex mode; client id 0x10005)
NOTE: ASMB rebuilding ASM server state
NOTE: ASMB rebuilt 1 (of 1) groups
NOTE: ASMB rebuilt 13 (of 13) allocated files
NOTE: fetching new locked extents from server
NOTE: 0 locks established; 0 pending writes sent to server
SUCCESS: ASMB reconnected & completed ASM server state

Again, user connected to database instance didn’t even noticed that something is happening with ASM.

Flex ASM enables for ASM instance to run on separate nodes than database servers. If ASM instance fails database will failover to another available ASM instance.

In case you are running <12c databases on your cluster you can still configure Flex ASM but you are required to configure local ASM instances on nodes. ASM instance failover won’t work for 10g or 11g databases.

Good reason to move towards 12c? ;-)