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Tablespaces:

Oracle Stores logically in tablespace and physically the data must be stored in Datafiles.

Datafiles must be created under the Tablespaces.

Tablespace is  a place where we can store store the tablespaces object such as tables,indexes.

A Tablespace must contain more than one Datafile.

The total number of storage space available in a tablespace is the sum of the disc size.

Tablespaces are  divided into 2 types

1) Small File Tablespace

2) Big File Tablespace

Small File Tablespace:

It contains the 1024 datafiles having 2 ^22 blocks these files restore time is less Datafiles can grow

upto 64GB.

BigFile Tablespace:

It contains Only one Datafile  having 2^32 blocks these files restore time is high Datafiles can grow

up to 128 TB.

Based on Space management the tablespaces are divided into 2 types


1)  Dictionary Managed  tablespace

2) Locally Managed Tablespace.

1) Dictionary Managed Tablespace :

• If the space allocation or deallocation information is referred in the data dictionary then such database are called Dictionary Managed Tablespace.

•  It contains tables that store information that is used to manage extent allocation and deallocation manually.
• Each segment has different storage clause. 

• LMT Manages its own extents maintaining a bitmap in each datafile  to keep track of the free or used status of blocks in that datafile.
• Each bit in a bit-map corresponds to a block or  a group of blocks