After Initial BLC Loading

Database

After Initial BLC Loading

As space saving initiative, we are applying BLC on certain tables in our Teradata system.

We are using queryband "SET QUERY_BAND='BLOCKCOMPRESSION=YES;' FOR SESSION;" to compress the data and insert into a table.After the initial load, we are dropping  the old table and renaming the compressed table as original.My question is after the  initial load, do we need to use the querybanding on a daily basis for the incremental loads on that table?Will be data inserted into that table be compressed  automatically , or we have to specify compression query band in the job session that loads data on a daily basis?

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Re: After Initial BLC Loading

The file system will notice that existing data blocks are compressed and compress new data, too. But when the table is truncated (DELETE ALL) there are no existing blocks and new data will be compressed on queryband.

Re: After Initial BLC Loading

Thanks Dieter:)

Teradata Employee

Re: After Initial BLC Loading

Hi Dieter, 

in our system BLC is enable on database level and vie Ferret , we have identfied the tables on whic BLC is enable.

now there is requirment to calculate the actual size of these tables without blc, Can some body help me how will can i extract actual size of BLC tables without out compression.

thanks,

Re: After Initial BLC Loading

If you are V15.10, the BLC compression % for a table can be found in DBC.StatsV under column BLCCompRatio