Purpose
Determines whether the file system automatically merges data blocks together on storage cylinders during full table modify operations. Merging several small data blocks into a single larger block can improve system performance by reducing disk I/O.
Field Group
File System
Valid Settings
| Setting | Description |
|---|---|
| TRUE | Automatic merging of data blocks is disabled. |
| FALSE | Automatic merging of data blocks is enabled. |
Default
FALSE
Changes Take Effect
After the DBS Control record has been written.
Usage Notes
During normal database operations, the data blocks that store table rows on cylinders can split and shrink, resulting in many blocks which are far smaller than the maximum allowed data block size. Full table modify operations for tables with several small data blocks require more disk I/O than would be required if the table rows were stored on fewer and larger data blocks. Teradata Database can merge the small data blocks of these tables automatically during full table modify operations, which can result in reduced I/O overhead and improved database performance.
Data block merging applies only to permanent and permanent journal tables.
If DisableMergeBlocks is TRUE, the MergeBlockRatio field is ignored.
Related Topics
| For more information on... | See... |
|---|---|
| Setting the maximum size of merged data blocks | MergeBlockRatio. |
| the MERGEBLOCKRATIO option of CREATE TABLE and ALTER TABLE | Teradata Vantage™ - SQL Data Definition Language Syntax and Examples, B035-1144. |