when-to-use-rebuild-vs-coalesce-vs-shrink

• Find out the table size

  SELECT owner, segment_name, segment_type, partition_name, ROUND(bytes/(1024*1024),2) SIZE_MB, tablespace_name 
  FROM DBA_SEGMENTS 
  WHERE SEGMENT_TYPE IN ('TABLE', 'TABLE PARTITION', 'TABLE SUBPARTITION', 
  'INDEX', 'INDEX PARTITION', 'INDEX SUBPARTITION', 'TEMPORARY', 'LOBINDEX', 'LOBSEGMENT', 'LOB PARTITION')
  --AND TABLESPACE_NAME LIKE 'COSTE%' 
  --AND SEGMENT_NAME LIKE 'P2010201%' 
  --AND partition_name LIKE 'P20100201%'
  --AND segment_type = 'TABLE'
  --AND OWNER = 'TARGET_POC' 
  --AND ROUND(bytes/(1024*1024),2) > 1000 
  ORDER BY bytes DESC;

  You can group by tablespace, owner and segment type and see the total space occupied in MBytes

  SELECT tablespace_name, owner, segment_type "Object Type",
     COUNT(owner) "Number of Objects",
     ROUND(SUM(bytes) / 1024 / 1024, 2) "Total Size in MB"
  FROM   sys.dba_segments
  WHERE  tablespace_name IN ('MPIS')
  GROUP BY tablespace_name, owner, segment_type
  ORDER BY tablespace_name, owner, segment_type;

• find out the usage of tablespace

  select df.tablespace_name "Tablespace",
  totalusedspace "Used MB",
  (df.totalspace - tu.totalusedspace) "Free MB",
  df.totalspace "Total MB",
  round(100 * ( (df.totalspace - tu.totalusedspace)/ df.totalspace))
  "Pct. Free"
  from
  (select tablespace_name,
  round(sum(bytes) / 1048576) TotalSpace
  from dba_data_files 
  group by tablespace_name) df,
  (select round(sum(bytes)/(1024*1024)) totalusedspace, tablespace_name
  from dba_segments 
  group by tablespace_name) tu
  where df.tablespace_name = tu.tablespace_name ;

• Shrink table
  alter table STATS$SQL_SUMMARY enable row movement;
alter table STATS$SQL_SUMMARY shrink space;

• Shrink index
  alter index STATS$SQL_SUMMARY_PK shrink space compact
alter index STATS$SQL_SUMMARY_PK shrink space;
alter index STATS$SYSSTAT_PK coalesce
alter index STATS$SQL_SUMMARY_PK rebuild

shrink space compact = coalesce

• Reference
  when-to-use-rebuild-vs-coalesce-vs-shrink-space
  深入理解重建索引
  Alter index coalesce VS shrink space
  alter index coalesce和alter index rebuild的区别