This subsection describes the rules for changing storage conditions.

(a) Maximum and minimum values

When you change storage conditions, you must observe the maximum and minimum values shown in the following table.

Table 13-25 Maximum and minimum values for the combine facility

Item	Maximum value	Minimum value	Result when the value is not within the range of the minimum and maximum values
Number of RDAREAs that can be combined in a single operation	16	2	Causes an error in ALTER TABLE.
Number of RDAREAs that are combined after execution of ALTER TABLE	1 (fixed)
Total number of RDAREAs resulting from combining	--	1

Legend:

--: Not applicable.

(b) Rules for combining

The RDAREAs to be combined must satisfy specific conditions. The following table shows under which conditions RDAREAs can be combined.

Table 13-26 Determination of whether RDAREAs can be combined

RDAREAs to be combined		Whether combinable	Description
The combination-target RDAREAs are specified in the table definition.		Y	RDAREAs can be combined.
The combination-target RDAREAs contain an RDAREA that is not specified in the table definition.		N	Causes an error in ALTER TABLE.
RDAREA with OTHERS specified#	Storage conditions have been specified for all RDAREAs.	Y	An example of combining an RDAREA with OTHERS specified is shown in Figure 13-56 Example of combining an RDAREA with OTHERS specified.
	There is an RDAREA with no storage condition specified.	N	Causes an error in ALTER TABLE. An example in which an RDAREA with OTHERS specified cannot be combined is shown in Figure 13-57 Example where an RDAREA with OTHERS specified cannot be combined.

Legend:

Y: Can be combined.

N: Cannot be combined.

#: For details about an RDAREA with OTHERS specified, see 13.12.9(2) RDAREA with OTHERS specified.

Figure 13-56 Example of combining an RDAREA with OTHERS specified

Figure 13-57 Example where an RDAREA with OTHERS specified cannot be combined

When storage conditions are specified, you can combine dummy RDAREAs with no entity. You can also integrate an RDAREA in a dummy RDAREA. Such a dummy RDAREA with no entity is called an RDAREA with OTHERS specified. RDAREAs with OTHERS specified are treated as RDAREAs with no storage condition specified during split or combine processing. The following describes how to use RDAREAs with OTHERS specified:

• You can delete existing storage conditions and create an RDAREA with no storage condition specified.
  By including an RDAREA with OTHERS specified in the combination-target RDAREAs, you can delete existing storage conditions and create an RDAREA with no storage condition specified. For an example, see Figure 13-56 Example of combining an RDAREA with OTHERS specified.
  
• You can delete RDAREAs with storage conditions specified.
  If combination-target RDAREAs include an RDAREA with no storage condition specified or an RDAREA with OTHERS specified, you can specify the RDAREA with OTHERS specified as the RDAREA resulting after combine processing. Because an RDAREA with OTHERS specified is treated as an RDAREA with no storage condition specified, you can delete an RDAREA with storage conditions specified by combining an RDAREA with OTHERS specified and the RDAREA with storage conditions specified. For an example, see 13.12.9(3) How to determine the combined RDAREA.
  

You specify the combined RDAREA in CHANGE RDAREA of ALTER TABLE. This RDAREA stores the data that satisfies all storage conditions for the combination-target RDAREAs. The resulting combined RDAREA might be one of the combination-target RDAREAs or a newly provided RDAREA.

Note that the RDAREAs might not be combined depending on the conditions during combine processing. This subsection describes the permitted and prohibited combinations of combination-target RDAREAs and post-combination RDAREA.

(a) Total number of post-combination RDAREAs

There is a condition on the total number of post-combination RDAREAs. The following table shows the relationship between the conditions during combine processing and the total number of post-combination RDAREAs.

Table 13-27 Relationship between the conditions during combine processing and the total number of post-combination RDAREAs

Condition during combine processing			Total number of post-combination RDAREAs
Condition for combination-target table	Condition for combination-target RDAREAs.		1	2 or more
There is an RDAREA with no storage condition specified.	There is an RDAREA with OTHERS specified.		N#1
	There is no RDAREA with OTHERS specified.	There is an RDAREA with no storage condition specified.	N (see Figure 13-63 Case where combine processing is not supported (part 1))	Y (see Figure 13-58 Case where combine processing is supported (part 1))
		There is no RDAREA with no storage condition specified.	--	Y (see Figure 13-59 Case where combine processing is supported (part 2))
There is no RDAREA with no storage condition specified.	There is an RDAREA with OTHERS specified.		N (see Figure 13-64 Case where combine processing is not supported (part 2))	Y (see Figure 13-60 Case where combine processing is supported (part 3))
	There is no RDAREA with OTHERS specified.		Y#2 (see Figure 13-61 Case where combine processing is supported (part 4))	Y (see Figure 13-62 Case where combine processing is supported (part 5))

Legend:

Y: Can be combined.

N: Cannot be combined.

--: Not applicable.

#1

If the combination-target table has an RDAREA with no storage condition specified, an RDAREA with OTHERS specified cannot be specified as a combination-target RDAREA.

#2

RDAREAs cannot be combined if an index has been defined for the combination-target table.

Figure 13-58 Case where combine processing is supported (part 1)

Figure 13-59 Case where combine processing is supported (part 2)

Figure 13-60 Case where combine processing is supported (part 3)

Figure 13-61 Case where combine processing is supported (part 4)

Figure 13-62 Case where combine processing is supported (part 5)

Figure 13-63 Case where combine processing is not supported (part 1)

Figure 13-64 Case where combine processing is not supported (part 2)

(b) When combining only RDAREAs with storage conditions specified

The following table lists and describes the specification conditions for the post-combination RDAREA and whether combine processing is supported (when only RDAREAs with storage conditions specified are to be combined).

Table 13-28 Specification conditions for the post-combination RDAREA and whether combine processing is supported (when only RDAREAs with storage conditions specified are to be combined)

Specification condition for post-combination RDAREA		Whether combine processing is supported
No combination-target RDAREA is used after combine processing.	One of the table storage RDAREAs is specified as the post-combination RDAREA.	N (RDAREA specification error)
	An RDAREA other than a table storage RDAREAs is specified as the post-combination RDAREA.	Y (see Figure 13-65 Case where combine processing is supported (part 6))
	An RDAREA with OTHERS specified is specified as the post-combination RDAREA.	N (see Figure 13-67 Case where combine processing is not supported (part 3))
A combination-target RDAREA is used after combine processing.		Y (see Figure 13-66 Case where combine processing is supported (part 7))

Legend:

Y: Can be combined.

N: Cannot be combined.

Figure 13-65 Case where combine processing is supported (part 6)

Figure 13-66 Case where combine processing is supported (part 7)

Figure 13-67 Case where combine processing is not supported (part 3)

(c) When an RDAREA with no storage condition specified is to be combined

The following table lists and describes the specification conditions for the post-combination RDAREA and whether combine processing is supported (when an RDAREA with no storage condition specified is to be combined).

Table 13-29 Specification conditions for the post-combination RDAREA and whether combine processing is supported (when an RDAREA with no storage condition specified is to be combined)

Specification condition for post-combination RDAREA		Conditions for table storage RDAREA after combine processing
		When there is an RDAREA with no storage condition specified	When there is no RDAREA with no storage condition specified
No combination-target RDAREA is used after combine processing.	One of the table storage RDAREAs is specified as the post-combination RDAREA.	N (RDAREA specification error)	--
	An RDAREA other than one of the table storage RDAREAs is specified as the post-combination RDAREA.	Y (see Figure 13-68 Case where combine processing is supported (part 8))	--
	An RDAREA with OTHERS specified is specified as the post-combination RDAREA.	Y (see Figure 13-69 Case where combine processing is supported (part 9))	--
A combination-target RDAREA is used after combine processing.		Y (see Figure 13-70 Case where combine processing is supported (part 10))	--

Legend:

Y: Can be combined.

N: Cannot be combined.

--: Not applicable.

Figure 13-68 Case where combine processing is supported (part 8)

Figure 13-69 Case where combine processing is supported (part 9)

Figure 13-70 Case where combine processing is supported (part 10)

(d) When an RDAREA with OTHERS specified is to be combined

The following table lists and describes the specification conditions for the post-combination RDAREA and whether combine processing is supported (when an RDAREA with OTHERS specified is to be combined).

Table 13-30 Specification conditions for the post-combination RDAREA and whether combine processing is supported (when an RDAREA with OTHERS specified is to be combined)

Specification condition for post-combination RDAREA		Conditions for table storage RDAREA after combine processing
		When there is an RDAREA with no storage condition specified	When there is no RDAREA with no storage condition specified
No combination-target RDAREA is used after combine processing.	An RDAREA with storage conditions specified is specified as the post-combination RDAREA.	N (OTHERS cannot be specified)	N (specified RDAREA is not a target of combine processing)
	An RDAREA other than one of the table storage RDAREAs is specified as the post-combination RDAREA.	N (OTHERS cannot be specified)	Y (see Figure 13-71 Case where combine processing is supported (part 11))
	An RDAREA with OTHERS specified is specified as the post-combination RDAREA.	N (OTHERS cannot be specified)	Y (see Figure 13-72 Case where combine processing is supported (part 12))
A combination-target RDAREA is used after combine processing.	An RDAREA with storage conditions specified is specified as the post-combination RDAREA.	N (OTHERS cannot be specified)	Y (see Figure 13-71 Case where combine processing is supported (part 11))
	An RDAREA with OTHERS specified is specified as the post-combination RDAREA.	N (OTHERS cannot be specified)	Y (see Figure 13-72 Case where combine processing is supported (part 12))

Legend:

Y: Can be combined.

N: Cannot be combined.

Figure 13-71 Case where combine processing is supported (part 11)

Figure 13-72 Case where combine processing is supported (part 12)

If a resource such as a partitioning key index has been defined for the combination-target table, you must combine not only the table storage RDAREAs but also the index storage RDAREAs. The following table shows the resources that must be combined at the same time.

The figure below shows an example of combining when a resource such as a partitioning key index has been defined for the table.

Table 13-31 Resources subject to combining when storage conditions are changed

Resource defined for the table	Combining method
Index	Combine so that the index storage RDAREAs have a 1-to-1 correspondence with the table storage RDAREAs.
Cluster key
Primary key
LOB column

Figure 13-73 Example of combining when a resource such as a partitioning key index has been defined for the table

The following rules apply to combine processing:

• If multiple resources have been defined, all resources are subject to combining.
• If the specification for combining is invalid, ALTER TABLE results in an error.

When ALTER TABLE is executed, data is normally deleted from a combination-target RDAREA. Data is also deleted from the following corresponding RDAREAs:

• Index data in index storage RDAREAs
• Lob data in LOB column storage RDAREAs
  

  Reference note

  The reason for deleting data from combination-target RDAREAs is as follows:

  • Combination-target RDAREAs might no longer be used after combine processing.

  Note that data is not deleted from RDAREAs that are not combination targets.

The following figure shows the data that is deleted during combine processing.

Figure 13-74 Data that is deleted during combine processing

(a) Case in which data is not deleted

If the following conditions are all satisfied, data can be retained because data in the combination-target RDAREA might be usable as is:

1. The combination-target RDAREA is to be used after combine processing.
2. The combination-target index storage RDAREA or LOB column storage RDAREA also satisfies condition 1.

If data is not to be deleted, you must specify WITHOUT PURGE in ALTER TABLE. If use of a combination-target RDAREA after combine processing is not specified but WITHOUT PURGE is specified, ALTER TABLE results in an error. The following figure shows the processing when WITHOUT PURGE is specified.

Figure 13-75 Processing when WITHOUT PURGE is specified

Explanation:

Because RDAREAs are combined into RD02, the data in RD02 (whose storage condition is ='B') is not deleted. The data in RD03 and RD04 (whose storage conditions are ='C' and ='D') is deleted.

Note

If data is saved with WITHOUT PURGE specified, and the pre-combination data is unloaded and then loaded into the post-combination RDAREA, that data is registered twice. Therefore, if you save data with WITHOUT PURGE specified, do not perform data unloading or data loading.

In the case of Figure 13-75, if the data in RD02 (whose storage condition is ='B') is unloaded and then loaded into the post-combination RDAREA, the data is registered twice.

(b) Notes about combining into an RDAREA with OTHERS specified

If combine processing is performed when both the following conditions are satisfied, there will be no RDAREA for storing pre-combination data:

• A combination-target RDAREA is an RDAREA with no storage condition specified or OTHERS specified.
• The data is to be combined into an RDAREA with OTHERS specified.

Figure 13-76 Case where there will be no RDAREA for storing data after combine processing (part 1) and Figure 13-77 Case where there will be no RDAREA for storing data after combine processing (part 2) show the cases where there will be no RDAREA for storing data after combine processing.

Figure 13-76 Case where there will be no RDAREA for storing data after combine processing (part 1)

Figure 13-77 Case where there will be no RDAREA for storing data after combine processing (part 2)