To monitor multiple databases, you may need to increase the JVM memory allocation size. Increased activity on the databases you are monitoring results in increased memory usage. 

Use one of the following commands to start the agent, and to initially allocate 1536 MB to the agent instead of the default of 64 MB. 

For Windows 64-bit

C:\java -Xmx1536m -Djava.library.path="<db_agent_home>\auth\x64" -jar <db_agent_home>\db-agent.jar

For Linux

% java -Xmx1536m -jar <db_agent_home>/db-agent.jar