16.10 - DictionaryDBSize - Teradata Database

Teradata Database Utilities

Product
Teradata Database
Release Number
16.10
Published
June 2017
Language
English (United States)
Last Update
2018-04-26
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Purpose

Specifies the maximum size for multirow data blocks in dictionary (database DBC) tables. Rows that are larger than DictionaryDBSize are stored in single-row data blocks, which are not limited by DictionaryDBSize.

Field Group

File System

Valid Values

42 through 2047 sectors for systems that use large cylinders.

18 through 512 sectors for systems that use small cylinders.

You can set DictionaryDBSize to USEPERMDBSIZE for both small and large cylinder systems. This value causes Teradata Database to use the current PermDBSize field setting for DictionaryDBSize.

A sector is 512 bytes.

Default

254 sectors

Setting this field to 0 causes Teradata Database to use the system default size for this type of data block.

Changes Take Effect

After a system initialization (sysinit) or an upgrade to a major xx.00 release.

Usage Notes

When database tables are initially populated, Teradata Database stores as many rows as possible into each data block, until the block reaches the size specified by the various DB size settings in DBS Control. As tables are subsequently modified, rows can grow such that the existing data blocks would exceed the maximum size. When this happens, the data block is split, and roughly half the rows are moved to a new data block, with the result that the original and new data blocks are each one half of the original size. The result of this type of growth and splitting is that data blocks for heavily modified tables tend to be about 75% of the maximum size defined in DBS Control.

If DBs are compressed, this setting applies to the size of the uncompressed DBs.

Systems initialized on Teradata Database 13.10 or later release use large cylinders. On large-cylinder systems, the minimum data block size is 42 sectors (21504 bytes).