Netscaler Pattern uses an SNMP query for getting the Failoverstatusid and maps it to operational status of the CI.
The SNMP query for getting the Failover status with the OID is: 188.8.131.52.4.1.59184.108.40.206.6
If you look for OID: 220.127.116.11.4.1.5918.104.22.168.6 in the Netscaler documentation or in the MIB browser you can see that: 0 - standalone, 1 - primary, 2 - secondary
Pattern will update the operational status of the load balancer based on the response from the query. If the SNMP query returns the value as 2, the load balancer is updated as non-operational.
For more information, see the NS-ROOT-MIB documentation.