Database failed to mount after reaching configured maximum database size

Failed to mount database "DB01". Error: An Active Manager operation failed. Error: The database action failed. 

Error: Database 'DB01' on server 'Exch01' cannot be mounted due to a previous error:
      
At '3/14/2019 9:41:57 AM' database copy 'DB01' on this server exceeded the configured maximum database size and service recovery was not attempted. Please increase the value of this registry key on the server hosting the active database copy before attempting to mount this database.

You may encounter this error on the Exchange Database if you are running Exchange Server on Standard edition and database size has reached the 1 TB.

To fix this issue you need to create the following registry entry on the exchange server for the database which we want to increase the database size limit.

"Database Size Limit in GB" 

The REG_DWORD needs to be created in the database GUID folder container, Get the database GUID using the following CMD.

(Get-MailboxDatabase DB01).guid

full key path:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\exch01\Private-<Database guid>

Set the value in GB in Decimal

After that, restart the Exchange Information Store service and the database should now be mounted, if not mounted then mount the database using the -Force switch.