Cant start dbase as No space left on device due to $USERS.dbf

[marrow]

Orace9.2
SQL> connect /as sysdba
ERROR:
ORA-09817: Write to audit file failed.
SVR4 Error: 28: No space left on device
ORA-09945: Unable to initialize the audit trail file
SVR4 Error: 28: No space left on device

On test system USERS.dbf has taken 12Gb of space and filled file-system to 100%. Should I simply delete offending USERS so our other database can startup, or... advice welcome

 

[marrow]

I released some space and was able to shutdown & restart databases OK. So I now need to address $users01.dbf and reduce size from 12GB to a normal size as space is still at almost 100%