Firebird Interview Question:

How to repair a corrupt Firebird database?

Submitted by: Administrator

Here's a short step-by-step walkthrough:

* disconnect users and disable incoming connections to the database
* make a copy of database file (or two copies) and work on that
* use GFIX with -v option to validate the database file
* use GFIX with -v and -f to do full validation

If problem is not too serious, you can try to backup the broken db and restore under a new name:

* use GFIX -mend to prepare corrupt database for backup
* use GBAK -b -g to backup the database. -g disables garbage collection (FAQ #41)
* use GBAK -c to restore backup to a new database.

If you succeed, you have fixed the problem and have a functional database. If not, you can try to create an empty database with the same structure and pump the data to it.

One of the reasons why backup or restore can fail is if some broken database triggers exist, and prevent connection to the database. For example, a database trigger might use some table which has a broken index, etc. To work around this, connect to database with isql tool using -nodbtriggers option and then disable those triggers. You can enable them later when you fix other problems and get a working database again.
Submitted by: Administrator