12.11 Specifying the no-split option
If any of the data types below is defined for a table and the actual data length of that data type is 256 bytes or greater, the system stores a row of data in multiple pages. The figure following the list shows the data storage method used to do this.
- Explanation:
- The variable-length character string data is stored in a page separate from the remaining data, adversely affecting the data storage efficiency. In these cases, use the no-split option to improve the data storage efficiency.
- Organization of this section
- (1) Criteria
- (2) Specification
- (3) Notes
(1) Criteria
If you specify the no-split option, the system stores one row of actual variable-length character string data in one page, even if the data length is 256 bytes or greater. The following figure shows the data storage method used when the no-split option is specified.
Figure 12-22 Data storage method used when the no-split option is specified
![[Figure]](figure/zu120157.gif)
- Explanation:
- An entire row of data is stored in the same page. Therefore, the data storage efficiency is better than when the no-split option is not specified.
(2) Specification
To specify the no-split option, specify the NO SPLIT option in the ALTER TABLE, CREATE TABLE, or CREATE TYPE SQL definition statement.
(3) Notes
- If the total length of a row of data exceeds the page length, data is split (one row of data is stored in multiple pages) even when the no-split option is specified.
- If you specify the no-split option when the actual variable-length character string data is 255 bytes or less, the column data becomes longer by one byte than when the no-split option is not specified.
- If the no-split option is specified, variable-length character columns will not be split even if the actual data length exceeds 256 bytes. In such a case, a page will be able to store fewer rows than if the no-split option were not specified. For this reason, if a retrieval does not collect column data from variable-length character columns for which an index scan determined the no-split option was appropriate, more pages may be accessed than if the no-split option were specified, and retrieval performance may be deteriorate. However, there is no effect when key scans and table scans are performed.