Oracle 12c New Features - Expert Consolidation in Oracle Database 12c - page 46

a new cluster resource of type ora.ASMNET1LSNR_ASM.lsnr will be created for the network. As you can imagine
Oracle will create multiple listeners if you specify multiple networks to be of type “ASM”. It is visible using the crsctl
utility as shown here:
[root@rac12node1 ~]# crsctl stat res -t
--------------------------------------------------------------------------------
Name Target State Server State details
--------------------------------------------------------------------------------
Local Resources
--------------------------------------------------------------------------------
ora.ASMNET1LSNR_ASM.lsnr
ONLINE ONLINE rac12node1 STABLE
ONLINE ONLINE rac12node2 STABLE
ONLINE ONLINE rac12node3 STABLE
The idea is strikingly simple: should an ASM instance to which databases are connected fail, the database will
dynamically reconnect to another ASM instance in the cluster. The following example demonstrates the new principle
in a three-node test cluster with the default cardinality reduced to two:
[grid@rac12node1 ~]$ srvctl modify asm -count 2
[grid@rac12node1 ~]$ srvctl status asm
ASM is running on rac12node3,rac12node1
The database started on node 2 will now not have its own ASM instance. It dutifully reports the fact in
the alert.log:
NOTE: ASMB registering with ASM instance as client 0xffffffffffffffff (reg:89854640)
NOTE: ASMB connected to ASM instance +ASM1 (Flex mode; client id 0x10007)
And it is also shown in the v$asm_client view. Here is the example of the first ASM instance:
SQL> select dg.name,c.instance_name,c.db_name,c.status
2 from v$asm_diskgroup dg, v$asm_client c
3 where dg.group_number = c.group_number
4 and c.db_name = 'RCDB1'
5 /
NAME INSTANCE_N DB_NAME STATUS
---------- ---------- -------- ------------
DATA RCDB12 RCDB1 CONNECTED
DATA RCDB11 RCDB1 CONNECTED
If an ASM instance such as the instance on node 3 crashes, the client will migrate to the surviving instance for the
time it takes to restart the other instance:
NAME INSTANCE_N DB_NAME STATUS
---------- ---------- -------- ------------
DATA RCDB11 RCDB1 CONNECTED
DATA RCDB13 RCDB1 CONNECTED
DATA RCDB12 RCDB1 CONNECTED