CA ARCserve Backup Agent for Open Files monitors the activity of all enabled backup clients. When it observes a file being opened by a client, it checks to see if the file is already in use by another program. If so, the agent waits until the file is in a safe state for the client to back it up. The agent determines this safe state by using the Write Inactivity Period. Various settings, affecting the way that the agent handles files, can be configured in the Files tab of the Configuration screen.
When the agent considers that it is safe to do so, it allows the client to proceed with opening and reading the file, even if the file is open and locked by another application. If the application subsequently makes changes to the file (or opens the file, if it was not previously open), the agent automatically preserves those parts of the file that the application changes, before the changes are implemented. It can then supply this 'preview' data to the backup client on demand. In this way, the client always receives, and backs up, file data corresponding to the original state of the file, but does not see any of the subsequent changes. However, all the changes made by the application are allowed to proceed unhindered, so that the file contents are always up to date.
Groups
Some applications, notably database systems, operate on a number of files simultaneously (for example, data files and index files). To ensure the integrity of backups of these files, the agent uses the concept of Groups, which are configured in the Configure Files screen of the agent. A group defines a number of files, optionally using wildcards, that must be backed up from a collective safe state. When the agent detects that a client is about to open any file in a group, it applies its safe state detection criteria to every file in the group. Only when every file is simultaneously in a safe state does it permit the client to proceed. Thereafter, the agent preserves preview data for all the files until every file has been accessed by the client (or until a configurable timeout occurs).
Renamed and Deleted Files
If an application tries to rename or delete a file while it is being backed up by a client, CA ARCserve Backup Agent for Open Files delays the rename or delete request for a period up to the File Sync Timeout setting for the file. If the client is still backing-up the file when the timeout expires, the agent passes the rename or delete request on to the server operating system, which may well fail it with a 'File In Use' error. Files that are frequently renamed or deleted are typically text, spreadsheet or similar files of relatively small size, which will be backed up before the timeout expires. A small delay typically goes unnoticed.
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