You might come across this error while trying to setup a fresh CI pipeline on Jenkins with SVN as repository :-
Caused by: org.tmatesoft.svn.core.SVNException: svn: E200030: BUSY
Check if the root folder of the job has a .svn folder(which is hidden). Delete this folder & try to checkout once again. This should solve your problem. Basically this .svn folder has some svn keys/credentials stored temporarily. These might come in conflict with some other keys which are already used on the machine for other purposes.
There is also a useful plugin which is available on Jenkins which is used in all of my jobs to solve this issue – The ‘Workspace Cleanup Plugin’. More info available @ https://wiki.jenkins-ci.org/display/JENKINS/Workspace+Cleanup+Plugin
Hope this post helps!