Arch command set - Revision library
Arch can optimize away expensive accesses to the archive. This is done with a revision library on the local disk. Not only does it speed up operation, you can also use arch's features when you are offline.
The most popular revisions (including changesets and the whole trees) may be stored in the library by the user's request. To learn more about the commands dealing with the revision library, see "tla help | grep library".