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Backup

Firebird comes with two utilities for backing up and restoring your databases: gbak and nbackup.Both can be found in the Firebird installation directory (Windows) or its bin subdirectory (Linux).Firebird databases can be backed up while users are connected to the system and going about their normal work.The backup will be taken from a snapshot of the database at the time the backup began.

Regular backups and occasional restores should be a scheduled part of your database management activity.

Warning

Except in nbackup’s lock mode, do not use external proprietary backup utilities or file-copying tools such as WinZip, tar, copy, xcopy, etc., on a database which is running.Not only will the backup be unreliable, but the disk-level blocking used by these tools can corrupt a running database.

Important

Study the warnings in the next section about database activity during restores!

More information about gbak can be found here (HTML and PDF version, same content):

The nbackup manual is here (again same content in HTML and PDF):

How to corrupt a database

The following sections constitute a summary of things not to do if you want to keep your Firebird databases in good health.

Disabling forced writes

Firebird is installed with forced writes (synchronous writes) enabled by default.Modifications are written to disk immediately upon posting.

It is possible to configure a database to use asynchronous data writes — whereby modified or new data are held in the memory cache for periodic flushing to disk by the operating system’s I/O subsystem.The common term for this configuration is forced writes off (or disabled).It is sometimes resorted to in an attempt to improve performance during large batch operations.

Disabling forced writes on Windows

The big warning here is: do not disable forced writes on a Windows server.It has been observed that the Windows server platforms do not flush the write cache until the Firebird service is shut down.Apart from power interruptions, there is just too much that can go wrong on a Windows server.If it should hang, the I/O system goes out of reach and your users' work will be lost in the process of rebooting.