In the Oracle RAC previous version we have worked with the option “misscount” of crsctl, which applies for all the servers because there was only one kind of servers, but in the new version of Oracle (12c) we have a new kind of RAC configuration, the “Flex Cluster”. With Flex Cluster we have two kinds of servers “Hub nodes” and “Leaf Nodes”, the Hub Nodes have the same concept of the normal nodes in the previous versions, however the Leaf Nodes are different. I will let Oracle Documentation define these servers:
Hub Nodes are similar to Oracle Grid Infrastructure nodes in an Oracle Clusterware standard Cluster configuration: they are tightly connected, and have direct access to shared storage. In an Oracle Flex Cluster configuration, shared storage can be provisioned to Leaf Nodes independent of the Oracle Grid Infrastructure.
Leaf Nodes are different from standard Oracle Grid Infrastructure nodes, in that they do not require direct access to shared storage, but instead request data through Hub Nodes. Hub Nodes can run in an Oracle Flex Cluster configuration without having any Leaf Nodes as cluster member nodes, but Leaf Nodes must be members of a cluster that includes at least one Hub Node.
Reference: https://docs.oracle.com/database/121/CWADD/bigcluster.htm#CWADD92560
With new kind of servers, we also have a new option to configure the maximum time that a Leaf node can be tolerated with heartbeat issues. This crsctl option is “leafmisscount” and it’s exactly the same than the “misscount” for Hub Nodes, but this is for Leaf Nodes.
Let’s see how does it work:
My Flex Cluster
Configuration
[[email protected] ~]# crsctl check cluster -all
**************************************************************
dg1:
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
**************************************************************
dg2:
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
**************************************************************
dg3:
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
**************************************************************
[[email protected] ~]#
[[email protected] ~]# crsctl get node role status -all
Node ‘dg1’ active role is ‘hub’
Node ‘dg2’ active role is ‘hub’
Node ‘dg3’ active role is ‘leaf’
[[email protected] ~]#
Checking the current value:
[[email protected] ~]$ crsctl get css leafmisscount
CRS-4678: Successful get leafmisscount 30 for Cluster Synchronization Services.
[[email protected] ~]$
How does it work with 30 secs:
[[email protected] ~]$ date
Fri Nov 14 16:03:54 EST 2014
–Stop connectivity between Leaf Node
and Hub Nodes
[[email protected] ~]# date
Fri Nov 14 16:04:01 EST 2014
[[email protected] ~]# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4535: Cannot communicate with Cluster Ready Services
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
[[email protected] ~]# date
Fri Nov 14 16:04:29 EST 2014
[[email protected] ~]# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4535: Cannot communicate with Cluster Ready Services
CRS-4530: Communications failure contacting Cluster Synchronization Services daemon
CRS-4534: Cannot communicate with Event Manager
[[email protected] ~]#
Now let’s increase the value to 600 sec:
[[email protected] ~]$ crsctl set css leafmisscount 600
CRS-4684: Successful set of parameter leafmisscount to 600 for Cluster Synchronization Services.
[[email protected] ~]$
Let’s confirm the value:
[[email protected] ~]$ crsctl get css leafmisscount
CRS-4678: Successful get leafmisscount 600 for Cluster Synchronization Services.
[[email protected] ~]$
The maximum value we can specify is 600:
[[email protected] ~]$ crsctl set css leafmisscount 3600
CRS-1671: The value for parameter leafmisscount is outside the allowed range of 1 to 600
[[email protected] ~]$
Let’s see how does it work with 600:
[[email protected] ~]# date
Fri Nov 14 16:19:54 EST 2014
–Stop connectivity between leaf
node and hub nodes
[[email protected] ~]# date
Fri Nov 14 16:24:01 EST 2014
[[email protected] ~]# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
[[email protected] ~]# date
Fri Nov 14 16:25:18 EST 2014
[[email protected] ~]# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
[[email protected] ~]# date
Fri Nov 14 16:27:30 EST 2014
[[email protected] ~]# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
[[email protected] ~]# date
Fri Nov 14 16:28:08 EST 2014
[[email protected] ~]# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
[[email protected] ~]# date
Fri Nov 14 16:29:04 EST 2014
[[email protected] ~]# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
[[email protected] ~]# date
Fri Nov 14 16:29:50 EST 2014
[[email protected] ~]# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4535: Cannot communicate with Cluster Ready Services
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
[[email protected] ~]# date
Fri Nov 14 16:30:10 EST 2014
[[email protected] ~]# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4535: Cannot communicate with Cluster Ready Services
CRS-4530: Communications failure contacting Cluster Synchronization Services daemon
CRS-4534: Cannot communicate with Event Manager
[[email protected] ~]#
1 Comment. Leave new
New leafmisscount Option in Flex Cluster 12c brings light to the server management engineers, as this consumes much time from the engineers to resolve the issue. you can get more tips on server management from https://iserversupport.com/ blog.