What is "checksum" in Teradata?

It basically specifies the (percentage) amount of data that should be used to compute the CHECKSUM for the table. 
It's used for detecting data corruption (bad blocks ?)
More % sample = More reliability in detecting errors, but to compute CHECKSUM over more data, you consume more CPU cycles and takes more time ...


The problem in the diskdrive and disk array...can corrupt the data....
these type of corrupted data cant be found easily..but queries against these corrupted data will get u wrong answers..we can find the corruption by means of scandisk and checktable.....
These errors will reduce the availability of the DWH.......This Kinda Errors is called DIsk I/o Errors In order to avoid this in TD we have the DIsk I/o Integrity Check....
by means of checksum for table level......this is a kinda protection technique by which we can select the various levels of corruption checking ..........
These checks are done by some integrity methods.....
This feature detects and logs the disk i/o errors 

TD give predefined data integrity levels check.....
default,low,end,medium,high....etc...

This checksum can be enabled.....using create table for table level.. DDL.
for system level use DBScontrol utilty to set the parameter

If u wanna more hands on then u ve to use the scandisk and checktbl utility....
u have to run the checktbl utility in level 3 so that it will diagnose the entire rows,byte by byte..