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Message Posted: Mon, 22 Sep 2014 @ 17:05:37 GMT

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Hi,

I'm not sure what you mean by 'compression values' for BLC.

BLC is not like Multi-Value Compression where you identify specific values to be compressed. Those values ARE stored in the table header.

Think of BLC as more like winzip on a pc. It doesn't look at specific data values in columns, it looks at bits/bytes which make up the entire data block and works at that level. The resulting, (hopefully smaller) data block is stored with other uncompressed data blocks on disk which is managed by the Teradata file system code.

BLC uses an industry standard compression algorithm - which one depends on the version of Teradata and what hardware you're using.

Does that help?

Cheers,

Dave

Ward Analytics Ltd - Information in motion (www.ward-analytics.com)

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