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Message Posted: Thu, 27 Jan 2011 @ 23:27:58 GMT

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Subj:   Re: Compressing infrequent values
From:   Campbell, William Dennis


Multi-value compression is meant to be used for frequently-occurring values, to maximize the space-saving benefit versus the setup time, but there are other limits.

Note the capacity for compression shown in the following quote from the 13.10 version of "Database Administration":

The number of MVC values you can list in a CREATE/ALTER TABLE statement is limited by:

* A maximum 255 values per column

* The allowable storage per column for the listed (uncompressed) values:

* ~7800 bytes per column for BYTE, KANJI1, and KANJISJIS data

* ~7800 characters per column for GRAPHIC, LATIN, or UNICODE data

* The 1 MB capacity of the table header to store a list of values to be compressed, minus the amount of space required to store other table-related information, such as database name, table name, subtable row format descriptions, PPI definitions, and restart information.

Dennis Campbell
Teradata Information Engineering

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