You do not need to drop the APM cluster ; it can be running and collecting metrics from Agent.
During the down time when Database is not available, you will see the below ERROR messages on the EM log, For 5 hours it might be tons of messages.
This is used mainlyby Team Center and CEM.
[ERROR] [WrapperSimpleAppMain] [Apm.Data.Model] APM Database is not reachable. Please check the connectivity…
org.springframework.jdbc.UncategorizedSQLException: Hibernate operation: Cannot open connection; uncategorized SQLException for SQL [???]; SQL state [null]; error code [0]; Connections could not be acquired from the underlying database!; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
1. You could set the AppMap property to "WARN" . To prevent the flooding of messages the following configuration setting can be made in the IntroscopeEnterpriseManager.properties file on the MOM
log4j.logger.Manager.AppMap=WARN, ,console,logfile.
2. You could disable the APM Center and CEM to avoid the ERROR messages
Disabling and Enabling APM Team Center
https://comm.support.ca.com/kb/_Disabling-and-Enabling-APM-Team-Center/KB000038314How to disable the CEM - Introscope integration?
https://comm.support.ca.com/kb/_How-to-disable-the-CEM-Introscope-integration/KB000015982