svn:needs-lock can be used to enforce exclusive locks on files (useful for binary files, for example). A file with the svn:needs-lock property defined can be modified by only one person at a time. When it’s checked out, the file will be read-only. If you want to modify the file, you need to use the Team > Lock menu option first. When you’re done, release the file with Team > Unlock, or just commit your changes. This action will release the lock and let other users obtain a lock on the file.
Subversion's locking feature exists ultimately to minimize wasted time and effort. Locking and unlocking exclusive right to change a file in the repository.
After the commit is finished, svn status shows that the lock token is no longer present in the working copy.

Cleo Clarify Studio - SVN Project Lock

To apply a lock it is as simple as three steps

• Step One: RIGHT CLICK on a Project and choose 'Properties'.
• Step Two: Choose 'SVN Info' in the right column. (see below)
• Step Three: Under Subversion defined properties, locate 'svn:needs-lock' (see below)
• Step Four: Synchronize project with SVN

Menu: Project->Properties

SVN Properties: Apply svn:needs-lock

Once svn:needs-lock is selected, CLICK on the Apply property recursively to: check box. This ensures this property is recursively applied to the packages and objects, within the Clarify 3 Project.