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Featured Database Articles


Posted May 7, 2002

Listen Software's How To: Tablespaces

By David Nishimoto

Adding a datafile

Indented lines in the following example are intended to be continuations of the lines above them. The lines are wrapped here for page formatting purposes. -Ed.

alter tablespace 
add datafile 
   size 30M;


alter tablespace user_data autoextend off;

Next and Maxsize are set to zero.

alter tablespace user_data
add datafile 'e:\{sid}\data\usr2.dbf';

alter tablespace user_data autoextend on max_size=40M;

Sets the maximum disk space allowed for automatic extension of the datafile.

Taking the Tablespace Online and Offline


alter tablespace user_data online;


alter tablespace user_data offline;

Hot Backup of a Tablespace

alter tablespace user_data begin backup;

alter tablespace user_data end backup;

This option does not prevent user from performing transactions.

Tablespace Coalese

alter tablespace user_data coalesce;

Coalesing gathers free segments. SMON usual cleans up free space.

Calculate Tablespace Size for Multiple Datafiles

Tablespace Byte Size
1 tablespace - multiple datafiles

Contribution by Stephen Mitchell

SELECT dfs.tablespace_name tablespace_name,
ddf.total_size total_size,
ddf.total_size - dfs.total_free total_used,
dfs.total_free total_free,
(ddf.total_size - dfs.total_free) / ddf.total_size * 100 cap,
dfs.total_chunks total_chunks,
dfs.largest_chunk largest_chunk
FROM (SELECT a.tablespace_name,
      SUM(a.bytes) / 1024 / 1024 total_free,
      COUNT(a.bytes) total_chunks,
      MAX(a.bytes) / 1024 / 1024 largest_chunk
      FROM dba_free_space a
      GROUP BY a.tablespace_name) dfs,
     (SELECT b.tablespace_name,
      SUM(b.bytes) / 1024 / 1024 total_size
      FROM dba_data_files b
      GROUP BY b.tablespace_name) ddf
WHERE dfs.tablespace_name = ddf.tablespace_name
ORDER BY dfs.tablespace_name

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