17.10 - mergeblockratio - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Definition Language Syntax and Examples

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1144-171K
Language
English (United States)

The merge block ratio to be used for this table when Vantage combines smaller data blocks into a single larger data block.

You can only specify a numeric merge block ratio for permanent base tables and permanent journal tables. You cannot specify a numeric merge block ratio for global temporary or volatile tables. You can specify either the DEFAULT MERGEBLOCKRATIO or the NO MERGEBLOCKRATIO options for global temporary and volatile tables.

If you do not specify this option, Vantage uses the value that is specified for the MergeBlockRatio parameter in the DBS Control record at the time a data block merge operation on the table begins.

This value of the merge block ratio for a table does not affect the resulting block size when only a single block is modified. Setting the merge block ratio to too high a value can cause the resulting merged block to require being split during subsequent modifications.

The system uses the merge block ratio you specify, depending on the setting for the DBS Control parameter DisableMergeBlocks. See Teradata Vantage™ - Database Utilities, B035-1102.

DisableMergeBlocks Description
FALSE The value you specify for MERGEBLOCKRATIO overrides the system-wide default setting for the DBS Control parameter MergeBlockRatio.
TRUE The system ignores all table-level settings for the merge block ratio and does not merge data blocks for any table in the system.
DEFAULT MERGEBLOCKRATIO
Vantage uses the value for MergeBlockRatio that is defined by the DBS Control record at the time a data block merge operation on this table begins.
MERGEBLOCKRATIO = integer
Vantage uses the value specified by integer as the merge block ratio when a data block merge operation occurs on this table.
The valid range for integer is from 1 through 100. The default value is 60.
PERCENT
Optional keyword to indicate that the value is a percentage.
NO MERGEBLOCKRATIO
NO MERGEBLOCKRATIO means that Vantage does not merge small data blocks for this table.