Using multiple tablespaces provides several Advantages
You can create Locally Managed or Dictionary Managed Tablespaces. In prior versions of Oracle only Dictionary managed Tablespaces were available but from Oracle ver. 8i you can also create Locally Managed tablespaces. The advantages of locally managed tablespaces are
Locally managed tablespaces track all extent information in the tablespace itself by using bitmaps, resulting in the following benefits:
To create a locally managed tablespace give the following command
SQL> CREATE TABLESPACE ica_lmts DATAFILE '/u02/oracle/ica/ica01.dbf' SIZE 50M EXTENT MANAGEMENT LOCAL AUTOALLOCATE;
AUTOALLOCATE causes the tablespace to be system managed with a minimum extent size of 64K.
The alternative to AUTOALLOCATE is UNIFORM. which specifies that the tablespace is managed with extents of uniform size. You can specify that size in the SIZE clause of UNIFORM. If you omit SIZE, then the default size is 1M. The following example creates a Locally managed tablespace with uniform extent size of 256K
SQL> CREATE TABLESPACE ica_lmt DATAFILE '/u02/oracle/ica/ica01.dbf' SIZE 50M EXTENT MANAGEMENT LOCAL UNIFORM SIZE 256K;
To Create Dictionary Managed Tablespace
SQL> CREATE TABLESPACE ica_lmt DATAFILE '/u02/oracle/ica/ica01.dbf' SIZE 50M EXTENT MANAGEMENT DICTIONARY;
A bigfile tablespace is a tablespace with a single, but very large (up to 4G blocks) datafile. Traditional smallfile tablespaces, in contrast, can contain multiple datafiles, but the files cannot be as large. Bigfile tablespaces can reduce the number of datafiles needed for a database.
To create a bigfile tablespace give the following command
SQL> CREATE BIGFILE TABLESPACE ica_bigtbs DATAFILE '/u02/oracle/ica/bigtbs01.dbf' SIZE 50G;