Exchange issues
Check the Database availability groups cmdlet - use to find out if exchange server is the Primary or Secondary
Get-DatabaseAvailabilityGroup
Exchange Log Drive filling
Enable circular logging to flush transaction logs. This will mean you will not have the logs to perform a database restore
Go to Exchange Management Console and then go into Organization configuration, then Mailbox. On the database management tab there will be the databases. Click on the database and select properties, then in the maintenance tab click to enable circular logging.
Then Dismount and remount the database, this will clear the transaction logs.
Once logs have been cleared by mounting the database with circular logging enabled you should then dismount, disable circular logging and mount again. Then get the backups sorted.