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|7.4 Chapter 4. Altering a Database

|Under the section "Altering a Table Space", the following new sections |are to be added:

|7.4.1 Adding a Container to an SMS Table Space on a Partition

| |

|You can add a container to an SMS table space on a partition (or node) |that currently has no containers.

|The contents of the table space are rebalanced across all containers. Access |to the table space is not restricted during the rebalancing. If you need |to add more than one container, you should add them all at the same time.

|To add a container to an SMS table space using the command line, enter |the following:

|   ALTER TABLESPACE <name>
|      ADD ('<path>')
|      ON NODE (<partition_number>)

|The partition specified by number, and every partition (or node) in the |range of partitions, must exist in the nodegroup on which the table space |is defined. A partition_number may only appear explicitly or within a range |in exactly one on-nodes-clause for the statement.

|The following example shows how to add a new container to partition number |3 of the nodegroup used by table space "plans" on a UNIX based operating |system:

|   ALTER TABLESPACE plans
|      ADD ('/dev/rhdisk0')
|      ON NODE (3)

|Following the section titled "Changing Table Attributes," |add the following sections:

|7.4.2 Altering an Identity Column

|

|Modify the attributes of an existing identity column with the ALTER TABLE |statement. For more information on this statement, including its syntax, refer |to the SQL Reference.

|There are several ways to modify an identity column so that it has some |of the characteristics of sequences.

|There are some tasks that are unique to the ALTER TABLE and the identity |column: |

|7.4.3 Altering a Sequence

|

|Modify the attributes of an existing sequence with the ALTER SEQUENCE statement. |For more information on this statement, including its syntax, refer to the SQL Reference.

|The attributes of the sequence that can be modified include: |

|There are two tasks that are not found as part of the creation of the sequence. |They are: |

|After restarting a sequence or changing to CYCLE, it is possible to generate |duplicate sequence numbers. Only future sequence numbers are affected by the |ALTER SEQUENCE statement.

|The data type of a sequence cannot be changed. Instead, you must drop the |current sequence and then create a new sequence specifying the new data type.

|All cached sequence values not used by DB2 are lost when a sequence is |altered.

|7.4.4 Dropping a Sequence

|

|To delete a sequence, use the DROP statement. For more information on this |statement, including its syntax, refer to the SQL Reference.

|A specific sequence can be dropped by using:

|   DROP SEQUENCE sequence_name 

|where the sequence_name is the name of the sequence to be dropped |and includes the implicit or explicit schema name to exactly identify an |existing sequence.

|Sequences that are system-created for IDENTITY columns cannot be dropped |using the DROP SEQUENCE statement.

|Once a sequence is dropped, all privileges on the sequence are also dropped.

|7.4.5 Switching the State of a Table Space

| |

|The SWITCH ONLINE clause of the ALTER TABLESPACE statement can be used |to move table spaces in an OFFLINE state to an ONLINE state if the containers |associated with that table space have become accessible. The table space is |moved to an ONLINE state while the rest of the database is still up and being |used.

|An alternative to the use of this clause is to disconnect all applications |from the database and then to have the applications connect to the database |again. This moves the table space from an OFFLINE state to an ONLINE state.

|To switch the table space to an ONLINE state using the command line, enter:

|   ALTER TABLESPACE <name>
|      SWITCH ONLINE

|7.4.6 Modifying Containers in a DMS Table Space

|

|DMS tables spaces are now created and resized in parallel, which offers |a performance benefit. The degree of parallelism is equal to the number of |prefetchers plus 1.


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