You can modify a table or table partition in any of the following ways. You cannot combine partition operations with other partition operations or with operations on the base table in one ALTER TABLE statement.

ADD PARTITION

Use ALTER TABLE ADD PARTITION to add a partition to the high end of the table (after the last existing partition). If the first element of the partition bound of the high partition is MAXVALUE, you cannot add a partition to the table. You must split the high partition.

You can add a partition to a table even if one or more of the table indexes or index partitions are marked UNUSABLE.

You must use the SPLIT PARTITION clause to add a partition at the beginning or the middle of the table.

The following example adds partition JAN98 to tablespace YR98:

ALTER TABLE sales
  ADD PARTITION jan98 VALUES LESS THAN( '980201' )
  TABLESPACE yr98;

DROP PARTITION

ALTER TABLE DROP PARTITION drops a partition and its data. If you want to drop a partition but keep its data in the table, you must merge the partition into one of the adjacent partitions.

If you drop a partition and later insert a row that would have belonged to the dropped partition, the row will be stored in the next higher partition. However, if you drop the highest partition, the insert will fail because the range of values represented by the dropped partition is no longer valid for the table.

This statement also drops the corresponding partition in each local index defined on table. The index partitions are dropped even if they are marked as unusable.

If there are global indexes defined on table, and the partition you want to drop is not empty, dropping the partition marks all the global, non-partitioned indexes, and all the partitions of global partitioned indexes as unusable.

When a table contains only one partition, you cannot drop the partition. You must drop the table.

The following example drops partition JAN96:

ALTER TABLE sales DROP PARTITION jan96;

EXCHANGE PARTITION

This form of ALTER TABLE converts a partition to a non-partitioned table and a table to a partition by exchanging their data segments. You must have ALTER TABLE privileges on both tables to perform this operation.

The statistics of the table and partition, including table, column, index statistics and histograms are exchanged. The aggregate statistics of the partitioned table are recalculated.

The logging attribute of the table and partition is exchanged.

The following example converts partition FEB97 to table SALES_FEB97:

ALTER TABLE sales
  EXCHANGE PARTITION feb97 WITH TABLE sales_feb97
   WITHOUT VALIDATION;

MODIFY PARTITION

Use the MODIFY PARTITION options of ALTER TABLE to

  • mark local index partitions corresponding to a table partition as unusable.
  • rebuild all the unusable local index partitions corresponding to a table partition.
  • modify the physical attributes of a table partition.

The following example marks all the local index partitions corresponding to the APR96 partition of the procurements table UNUSABLE:

ALTER TABLE procurements MODIFY PARTITION apr96
  UNUSABLE LOCAL INDEXES;

The following example rebuilds all the local index partitions which were marked UNUSABLE:

ALTER TABLE procurements MODIFY PARTITION jan98
  REBUILD UNUSABLE LOCAL INDEXES;

The following example changes MAXEXTENTS for partition KANSAS_OFF:

ALTER TABLE branch MODIFY PARTITION kansas_off
  STORAGE(MAXEXTENTS 100) LOGGING;

MOVE PARTITION

This ALTER TABLE option moves a table partition to another segment. MOVE PARTITION always drops the partition's old segment and creates a new segment, even if you do not specify a new tablespace.

If partition_name is not empty, MOVE PARTITION marks all corresponding local index partitions and all global non-partitioned indexes, and all the partitions of global partitioned indexes as unusable.

ALTER TABLE MOVE PARTITION obtains its parallel attribute from the PARALLEL clause, if specified. If not specified, the default PARALLEL attributes of the table, if any, are used. If neither is specified, it performs the move without using parallelism.

The PARALLEL clause on MOVE PARTITION does not change the default PARALLEL attributes of table.

The following example moves partition STATION3 to tablespace TS097:

ALTER TABLE trains
  MOVE PARTITION station3 TABLESPACE ts097 NOLOGGING;

MERGE PARTITION

While there is no explicit MERGE statement, you can merge a partition using either the DROP PARTITION or EXCHANGE PARTITION clauses. You can use either of the following strategies to merge table partitions.

If you have data in partition PART1, and no global indexes or referential integrity constraints on the table, PARTS, you can merge table partition PART1 into the next highest partition, PART2.

To merge partition PART1 into partition PART2:

  1. Export the data from PART1.

 
  • Issue the following statement:
    ALTER TABLE PARTS DROP PARTITION PART1;
  • Import the data from Step 1 into partition PART2.

Note: The corresponding local index partitions are also merged

Another way to merge partition PART1 into partition PART2:

  1. Exchange partition PART1 of table PARTS with "dummy" table PARTS_DUMMY.

 
  • Issue the following statement:
    ALTER TABLE PARTS DROP PARTITION PART1;
  • Insert as SELECT from the "dummy" tables to move the data from PART1 back into PART2.

SPLIT PARTITION

The SPLIT PARTITION option divides a partition into two partitions, each with a new segment, new physical attributes, and new initial extents. The segment associated with the old partition is discarded.

This statement also performs a matching split on the corresponding partition in each local index defined on table. The index partitions are split even if they are marked unusable.

With the exception of the TABLESPACE attribute, the physical attributes of the LOCAL index partition being split are used for both new index partitions. If the parent LOCAL index lacks a default TABLESPACE attribute, new LOCAL index partitions will reside in the same tablespace as the corresponding newly created partitions of the underlying table.

If you do not specify physical attributes (PCTFREE, PCTUSED, INITRANS, MAXTRANS, STORAGE) for the new partitions, the current values of the partition being split are used as the default values for both partitions.

If partition_name is not empty, SPLIT PARTITION marks all affected index partitions as unusable. This includes all global index partitions as well as the local index partitions which result from the split.

The PARALLEL clause on SPLIT PARTITION does not change the default PARALLEL attributes of table.

The following example splits the old partition STATION5 creating a new partition for STATION9:

ALTER TABLE trains
  SPLIT PARTITION STATION5 AT ( '50-001' )
  INTO ( PARTITION station5 TABLESPACE train009 (MINEXTENTS 2),
         PARTITION station9 TABLESPACE train010 )
  PARALLEL ( DEGREE 9 );

TRUNCATE PARTITION

Use TRUNCATE PARTITION to remove all rows from a partition in a table. Freed space is deallocated or reused depending on whether DROP STORAGE or REUSE STORAGE is specified in the clause.

This statement truncates the corresponding partition in each local index defined on table. The local index partitions are truncated even if they are marked as unusable. The unusable local index partitions are marked valid, resetting the UNUSABLE indicator.

If there are global indexes defined on table, and the partition you want to truncate is not empty, truncating the partition marks all the global non-partitioned indexes, and all the partitions of global partitioned indexes as unusable.

If you want to truncate a partition that contains data, you must first disable any referential integrity constraints on the table. Alternatively, you can delete the rows and then truncate the partition.

The following example deletes all the data in the part_17 partition and deallocates the freed space:

ALTER TABLE shipments
  TRUNCATE PARTITION part_17 DROP STORAGE;