FirstBackup can be configured to retry open or locked files. If the file remains locked during the retry period, it will be backed-up during the next scheduled backup. In most cases, this is sufficient.  

Standard Open File Support
One feature of FirstBackup that is often overlooked is its ability to backup data files while the file is open by an application.  This is made possible though the use of a sophisticated processing engine that can create a "snapshot" of an open file permitting activity to continue without interruption.  This particular open file support is limited to data files that are not opened "exclusively".  Examples of files that can be backed up by FirstBackup while open are:

• MS-Word
• MS-Excel
• MS-Access
• QuickBooks
• PeachTree
• MYOB
• GoldMine
• ACT
• most xBASE applications
• Quicken
• MS-Money
• ... and most other desktop-type applications found on the market today.

In every case, however, the data files of these applications must be opened in "shared" mode (which is normally the default).

The exception is transactional-intensive environments where large-scale Relational Database Management Systems (RDBMS) like SQL Server, or E-mail systems like Microsoft Exchange Server are utilized.  In these applications, the data files are "locked" for exclusive access - meaning that only the native application engine can access the data.

As is often the case, applications like SQL Server and Oracle incorporate functionality that permit live data to be "staged" prior to backup - without shutting down the database server.  Exchange data can also be “staged” with the assistance of the EXMerge utility. This staged data can then be successfully backed-up by FirstBackup's standard open file support, and access can continue to occur to the live data without interference.

See:
How do I backup my Microsoft Exchange Server?

How do I backup my SQL Server?

Optional Open File Support

In nearly all cases, FirstBackup's standard open file support along with the available utilities to “stage” live databases prior to backup is adequate. The FirstBackup support team can assist you with setup and configuration options. In rare cases, the use of the FirstBackup Open File Manager plug-in application may be required.  We suggest that you fully understand and exhaust all standard options prior to investing additional time and money setting up a dedicated open file backup solution.