Preventing application database connections from automatically activating a database after db2start.

Cause

Often, during maintenance events, a database is deactivated and the database-instance is stopped but the application is not stopped and will continue to attempt to establish a connection to the database while the database is under maintenance, this is not a problem in itself.
Later after maintenance completes and the database-instance is restarted and the database is activated, the application's attempt to establish a database connection will be successful.

However, there is a timing window where, after maintenance completes and the database-instance is started but before the database is activated, an application's database connection attempt can come in and automatically start database activation before a DBA has explicitly activated it. Since database activation can sometimes take several minutes, the application might timeout before the activation completes, and rollback the database activation. If the number of application threads attempting to connect to the database is very large, they may repeatedly start database activation ahead of the DBA's request to explicitly activate the database, and repeatedly timeout and rollback the activation.
This can cause a repeated loop of automatic database activation and timeout/rollback, while the DBA's explicit request to activate the database appears to hang.