DB2 Table Space
Table space is nothing but the space where the tables are stored.
A table space is a set of volumes or disks where the tables actually stored.
Table space contains all the tables in the database.
One table space can contain one or more tables.
One table space can be stored on more than one VSAM file.
Table space can be divided into equal parts, called as pages.
One operation on database can read one page at a time.
To create the storage group, user required CREATETS privilege is required apart from the above two authorities mentioned in storage space and database.
CREATE TABLESPACE is used to create table space.
CREATE TABLESPACE table-space-name IN database-name USING STOGROUP stogroup-name PRIQTY integer SECQTY integer ERASE NO/YES FREEPAGE 0/integer PCTFREE 5/smallint MAXPARTITIONS integer NUMPARTS integer PARTITION integer using-block/free-block SEGSIZE integer BUFFERPOOL bpname CLOSE YES/NO COMPRESS NO/YES LOCKMAX SYSTEM/integer LOCKSIZE ANY/TABLESPACE/TABLE/PAGE/ROW MAXROWS integer SEGSIZE integer
Let’s see the options one by one.
Name of the table space that is going to create.
Name of the database table under which the table space is going to create.
Name of the stored group under where the database existed.
PRIQTY is nothing but the primary quantity of space allocation.
PRIQTY should be always positive numeric value or -1.
SECQTY is nothing but the secondary quantity of space allocation.
SECQTY should be always positive numeric value or -1.
Specifies that whether the data needs to be erased or not during the deletion of the table space.
ERASE have YES & NO as a valid options.
Specifies how to leave the page as a free space in table space when it is partitioned or reorganized.
FREESPACE value must be in between 0 to 255.
The default value is 0, if the FREESPACE not provided during the declaration.
Specifies how to leave the page as a free space in table when it is loaded or reorganized.
PCTFREE value must be in between 0 to 99.
PCTFREE does not applies to table spaces.
Specifies that table space is a partition by growth table space.
MAXPARTITIONS must be in the range 0 to 4096.
MAXPARTITIONS value in the multiples of Giga bytes.
NUMPARTS used to specify number of partitions.
NUMPARTS only specifies for partitioned table spaces.
Specifies which partition is the using-block or free-block applies.
PARTITION value starts from 1 to NUMPARTS specified value.
Identifies which buffer pool used for table space.
Determines the page size of the table space.
Specifies the action to be taken when the limit of open data sets reached to its maximum.
The valid values are YES and NO.
Specifies the compression applies for the rows in table space or not.
The Valid values are YES and NO.
Specifies the maximum number of locks can hold simultaneously.
If 0 specifies, the locks will not be counted.
Specifies the size of locks within the table space.
DB2 uses any lock size specified.
Valid values are ANY/TABLESPACE/TABLE/PAGE/ROW
Specifies the max number of rows that need to placed per page.
The range can be from 1 to 255.
If nothing is specified, the default value is 255.
Specifies the number of pages assigned to the segment.
SEGSIZE has the range from 0 to 64 but multiples of 4.
SEGSIZE specifies the segmented table space.
SEGSIZE values can be in between 0 to 64 but multiples of 4.
Table space types:
Table spaces are of three types.
- Simple table space
- Segmented table space
- Partitioned table space
Let’s discuss about one by one in detail.
1. Simple table space:
Table space will be represented as pages and data will be stored in the form of pages.
More than one table can be stored in the table space.
Page contains all the table rows in which order they inserted into the table.
The rows from different tables can be stored in one page.
Simple table space concept explained in detail here .
2. Segmented table space:
Table space will be represented as Segments and data will be stored in the segments.
All the segments are of same size.
Segment’s is nothing but the set of pages.
The page number can be defined by SEGSIZE during the TABLESPACE definition.
Segmented table space concept explained in detail here .
3. Partitioned table space:
Table space will be represented as partitions.
Partition is a storage unit used to store the table rows.
Only one table can be stored for partition.
Each partition can contain one data set.
Partitioned table space concept explained in detail here .
DB2 Database DB2 Simple Table Space