It is not possible to do local commits with Subversion.
This is because, as a centralized version control system, your local working copy does not have all the information the server has about past revisions, log entries, etc. which it would have had if it was a Distributed Version Control System (DVCS).
A subversion working copy contains a copy of all files as they were checked out so you can revert changed files without contacting the server.
If you really want to do local commits you should have a look at SVK, which is built on top of Subversion and provides DVCS like features.