SnapshotCM In Depth: Discard Revision

Starting with the 1.84.2 release, SnapshotCM supports discarding inactive revisions and freeing space associated with them. This can be useful for freeing significant disk space taken up by large revisions (like release packages or .exe files) which, after a certain point in a project, no longer have a purpose for being. It can also be used for more general cleanup, such as removing inactive revisions older than a given date.

The first thing to understand about this feature is that revisions which are active cannot be removed. A revision is considered to be active if it is

• referenced by any snapshot,
• the latest revision, or
• a branch or merge point in the history.

Active revisions are simply skipped if selected for discard. This allows selecting a range of revisions (like all revisions, or everything older than a certain date) to have just the inactive ones removed.

The history record, change comment and associated file contents are removed when a revision is discarded: It can not be recovered. Removing a revision does not change the numbering of other revisions. Therefore, after a revision is removed, the history numbering will have gaps.

The discard operation requires administration write permissions, making it unavailable to most users.

The discard revision functionality is a new option on the Active History dialog, and allows selecting a contiguous range of revisions. For general cleanup, the functionality is available from the wremove(1) command, where revisions older than a given date also can be specified.

Example Command

To remove all inactive revisions older than a given date from jar files in the source hierarchy, run:

wremove -O "2010/11/01" -j '*.jar' -R source