17.00 - MERGEBLOCKRATIO - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Definition Language Syntax and Examples

Product
Advanced SQL Engine
Teradata Database
Release Number
17.00
Release Date
September 2020
Content Type
Programming Reference
Publication ID
B035-1144-170K
Language
English (United States)

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


DEFAULT
The value for MergeBlockRatio that is defined by the DBS Control record at the time a data block merge operation on this table begins. 
You can specify DEFAULT MERGEBLOCKRATIO for global temporary and volatile tables.
Whether Vantage uses the merge block ratio you specify depends on the setting for the DBS Control parameter DisableMergeBlocks.
  • If DisableMergeBlocks is FALSE and you specify a MERGEBLOCKRATIO, the system uses the value you specify. If you do not specify a MERGEBLOCKRATIO, the system uses the system-wide default setting for the DBS Control parameter MergeBlockRatio.
  • If DisableMergeBlocks is 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.
integer PERCENT
Merge block ratio when a data block merge operation occurs on this table, where integer is value from 1 through 100. The default value is 60.
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. This value of the merge block ratio does not affect the resulting block size when only a single block is modified. Setting the merge block ratio for a table to too high a value can cause the resulting merged block to require splitting during subsequent modifications.
PERCENT is an optional keyword to indicate value is a percentage.
NO
Data blocks for the table are not merged when Vantage combines smaller data blocks into a single larger data block.

You can specify NO MERGEBLOCKRATIO options for global temporary and volatile tables.