If you’re getting a ‘svn: Can’t find a temporary directory: Internal error’ error while using subversion, check the disk space on the server:
$ df
You’re more than likely out of space.
[dave@dev2:~/]$ df Filesystem 1K-blocks Used Available Use% Mounted on /dev/vg0-rootvol 73608360 73605908 0 100% /

I have the same problem.
I deleted some unused folders and files.
But how to increase the log file size when it reached the limitation:
/dev/vg0-rootvol 73608360 73605908 0 100%
Or perhaps your svnserve session needs to be restarted. This is all that was required to get my setup working again.