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 ; 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
2. You could disable the APM Center and CEM to avoid the ERROR messages
Disabling and Enabling APM Team Centerhttps://comm.support.ca.com/kb/_Disabling-and-Enabling-APM-Team-Center/KB000038314
How to disable the CEM - Introscope integration?https://comm.support.ca.com/kb/_How-to-disable-the-CEM-Introscope-integration/KB000015982