When you upgrade VAIM from 12.8 to 12.9 are you then forced to upgrade sysedge agents? We are currently running VAIM 12.8 with 5.8 agents. I don't think this would be the case i just wat to be sure VAIM 12.9 will manage 5.8 agents without issue.
The upgrade of the agent is usually enforced if you are running the VAIM upgrade on the manager.
The VAIM 12.9 manager can monitor SystemEDGE 5.8 agents.
To clarify and expand on Mohindra.Singh's response, only the agent on the VAIM manger will be upgraded when you perform the installation/upgrade. The upgrade of the manager does not force all agents to be upgraded. The upgraded manager can manage the older agents just fine. The upgrade will also lay down new deployment packages, so if desired you can push out agent upgrades from the VAIM server -- again, this is optional.