Had a nice issue - which demonstrated that looks can be deceiving. My colleague asked me to increase the size of a certain tablespace as it was full. I added a datafile in ASM for this tablespace but put it on autoextend = ON . He complained that it was still on 100 % full. A second I thought I messed up things (happens to the best :-) Then another look solved the problem: The query - which apparently was used in a lot of Nagios installations - checked only the datafiles which were on autoextend = no . The following query was used in Nagios. select d.tablespace_name "TABLESPACE", sum(d.bytes)/1048576 "SIZE (M)", 100 -(nvl(round((FREESPCE/(sum(d.bytes)/1048576))*100),0)) "USED (%)" FROM dba_data_files d, ( SELECT round(sum(f.bytes)/1048576,2) FREESPCE, f.tablespace_name Tablespc FROM dba_free_space f GROUP BY f.tablespace_name) WHERE d.autoextensible IN 'NO' AND d.tablespace_name = Tablespc (+) group by d.tablespace_name,FREESPCE,d.autoextensible o...