svn import error : Could not write svndiff to temp file: There is not enough space on the disk

Update: the OP itsraja finally found the $TMPDIR environment variable wasn't set (after some advices from zerkms in the comments above)

Sorry, I was searching in SVN's.
I haven't set anything as temporary directory, it seems. When echoed $TMPDIR, it is empty.
I believe it uses /tmp directory and it has enough space.
I set $TMPDIR, and the issue fixed, thanks

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Initial answer:

According to this post (for a Windows client, but the idea is still valid for an Unix client):

Using Subversion (via Tortoise, incidentally), I recently got this error:

svn:

Can't set position pointer in file 'C:\WINDOWS\TEMP\report.tmp':

There is not enough space on the disk.

This means you have run out of space on your server.
Sounds straight forward, but it took a while fooling around on the client

It could be a similar problem in your case (if you do have space left locally).

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Or it could be an ACL (access rights) issue on the tmp directory as described here:

Subversion uses an APR function (which we donated to that project) for finding a temporary directory.
It does so by trying to find a writable directory using the following search path:

      $TMP
      $TEMP
      $TMPDIR
      "C:\TEMP" (windows only)
      "SYS:\TMP" (netware only)
      "/tmp"
      "/var/tmp"
      "/usr/tmp"
      P_tmpdir (POSIX define)
      `pwd`

Do you have one of those first three environment variables set to a non-writable location?