When a commit fails due to someone else's locks, it's fairly easy to learn about them. The easiest of these is svn status --show-updates :

$ whoami
sally

$ svn status --show-updates
M              23   bar.c
M    O         32   raisin.jpg
       *       72   foo.h
Status against revision:     105

In this example, Sally can see not only that her copy of foo.h is out-of-date, but that one of the two modified files she plans to commit is locked in the repository. The O symbol stands for “Other”, meaning that a lock exists on the file, and was created by somebody else. If she were to attempt a commit, the lock on raisin.jpg would prevent it. Sally is left wondering who made the lock, when, and why. Once again, svn info has the answers:

$ svn info https://svn.example.com/repos/project/raisin.jpg
Path: raisin.jpg
Name: raisin.jpg
URL: https://svn.example.com/repos/project/raisin.jpg
Repository UUID: edb2f264-5ef2-0310-a47a-87b0ce17a8ec
Revision: 105
Node Kind: file
Last Changed Author: sally
Last Changed Rev: 32
Last Changed Date: 2005-01-25 12:43:04 -0600 (Tue, 25 Jan 2005)
Lock Token: opaquelocktoken:fc2b4dee-98f9-0310-abf3-653ff3226e6b
Lock Owner: harry
Lock Created: 2005-02-16 13:29:18 -0500 (Wed, 16 Feb 2005)
Lock Comment (1 line):
Need to make a quick tweak to this image.

Just as svn info can be used to examine objects in the working copy, it can also be used to examine objects in the repository. If the main argument to svn info is a working copy path, then all of the working copy's cached information is displayed; any mention of a lock means that the working copy is holding a lock token (if a file is locked by another user or in another working copy, svn info on a working copy path will show no lock information at all). If the main argument to svn info is a URL, then the information reflects the latest version of an object in the repository; any mention of a lock describes the current lock on the object.

So in this particular example, Sally can see that Harry locked the file on February 16th to “make a quick tweak”. It being June, she suspects that he probably forgot all about the lock. She might phone Harry to complain and ask him to release the lock. If he's unavailable, she might try to forcibly break the lock herself or ask an administrator to do so.