The failover mode specifies when and how a logical cluster runs on failover instances.
Use sp_cluster logical, "set" to specify the failover mode. Values are:
instance – specifies that whenever an online instance fails (whether a base or failover instance), it is replaced with a failover instance on a 1:1 basis. For example, suppose logical cluster “SalesLC” runs on instances “ase1” and “ase2” with “ase3” and “ase4” as failover instances, and the failover mode is “instance.” If “ase1” fails, “ase3” comes online, and the cluster runs on “ase2” and “ase3” (or “ase4”, depending on the relative workload of the two failover instances). instance is the default value.
group – specifies that base instances are replaced only when all base instances fail and that all failover instances then come online. Suppose the failover mode for “SalesLC” is “group.” If “ase1” fails, the cluster continues to run on “ase2”. No failover instances are brought online. However, if both “ase1” and “ase2” fail, then the cluster runs on “ase3” and “ase4”.
You can also designate multiple failover groups, so that even if instances in the first failover set fail, another set of failover instances is available to come online.
For example, to set the failover mode for “SalesLC” to “group”, enter:
sp_cluster logical, "set", SalesLC, failover, "group"
