As of Foglight V5.7.5.3 the release notes for most agent cartridges contain information under the "Upgrade and Compatibility" section indicating whether the agent is FglAM HA compatible.
The DB2 (5.6.10.7 and later) and SQL Server (5.7.5.1 and later) agents are supported in a FglAM HA configuration.
Please refer to KB 331743 on configuring Sybase agents to be supported in a HA configuration.
The Nexus agent is not currently FglAM HA aware but the nexus has supported an HA like feature for some time, it’s only the FglAM HA the Nexus doesn’t support. Because Nexus is itself an agent controller and doesn’t directly collect data, there is no benefit to supporting a FglAM HA configuration.
A user can create two nexus agents on separate FglAMs, and configure the java / .net agents to fail over to the second instance if the nexus fails. The agents need to know the address of both the Nexus agents. The "Understanding Nexus and Agent-Nexus Connections" section in the Java EE and .Net Installation guides has details on this. If the java agents know of two Nexus they will attempt to connect the first one available and will loop through the list until they can connect to any Nexus.
Enhancement request CAC-758 has been submitted to Development for consideration in a future release of Foglight.
Document enhancement request FDOC-7510 was implemented in Foglight V5.7.5.3.