You are logging into the system processor of the array which is basically a Solaris machine. Among other things, user logins are logged by Solaris, and the Filesystem full is preventing the entry from being written and therefore the login cannot proceed. This is normal Solaris behavior. You might try logging in through the console serial port but if memory serves me right, the only way out is boot to single user in order to clean up the root file system to allow login again.
P.S. You might want to try MOS Community next time if you need quicker response to your question.