This script lists the tablespace which cannot extent causing tablespace full.
select a.owner||'.'||a.segment_name "Segment Name",
a.segment_type "Segment Type",
a.bytes/1024/1024 "Size(MB)",
a.next_extent/1024/1024 "Next Extent",
a.tablespace_name "Tablespace Name"
from sys.dba_segments a
where a.tablespace_name not like 'T%MP%' -- Exclude TEMP tablespaces
and next_extent * 1 > ( -- Cannot extend 1x, can change to 2x...
select max(b.bytes)
from dba_free_space b
where a.tablespace_name = b.tablespace_name)
order by 3 desc;
