I get the error below when I run / execute an Explain Plan.
ORA-00604: error occurred at recursive SQL level 1 ORA-01536: space quota exceeded for tablespace ‘USERS’
Ensure the Plan Table your Toad is using exists, valid, and can use enough space in the tablespace or give unlimited tablespace rights.
Setting Toad to use the PLAN_TABLE from SYS schema via View menu | Toad Options | Oracle | General | Explain Plan can resolve the issue as well.