When backing up the database, if the software crashes, and you cannot access the database anymore with a message stating “Database *full path to database* shutdown”.. This could be due to the database being corrupted. The database was shutdown by Firebird. 

To access it again, you need to re-open the database. For that follow these steps:

    Step 1. Go to command prompt

    Step 2. Enter: “cd <full path to folder containing the gfix application of Firebird>”. Example: “cd C:\Program Files (x86)\Firebird\Firebird_2_1\bin”

    Step 3. Enter: gfix  -user "SYSDBA" -password "masterkey"  -online <enter_full_path_to_database>

Example: if my database MDB031.fdb is in Cà ProgramData à THORASYS à Database, the command will look like this:

“gfix  -user "SYSDBA" -password "masterkey"  -online C:\ProgramData\THORASYS\Database\MDB031.fdb”