Some Useful Data Dictionary VIEWS

Table spaces


dba_tablespacesuser_tablespaces 

Tablespace Quotas

dba_ts_quotas
user_ts_quotas
Data Files

dba_data_files
v$backup_datafile
v$datafile
v$datafile_copy
v$datafile_header
Free Space

dba_free_space
Segments

dba_segments
v$segment_statistics
Extents

dba_extents
Blocks

v$database_block_corruption

Groups

dba_tablespace_groups
SYSAUX Tablespace

v_$sysaux_occupants
Temp Tablespace

dba_temp_files
Undo Tablespace

dba_rollback_segs
dba_undo_extents
v$rollstat
v$undostat
Transportable Tablespaces

transport_set_violations