I wanted to know the significance of the checksum option in table definition. Can someone explain this to me?

Re: CheckSum


CheckSum is used to check the Disk I/O Integrity Check.....Problems originating in disk drive and disk array can also corrupt the data,
this kind of error will be in block and sector level .

These are the common orgins for the disk i/o corruption encountered in user data.Inorder to protect against this kinda coruptions TD permits to select the level of Disk I/O Integrity check in the Table level and also in System Level.

Re: CheckSum

Thanks for your immediate response. But, This is what I found in the manual too.

I want more details on this. I would like to know what the Disk I/O corruptions means and what the integrity means in this context.

How does specifying checksum help when it is defined for a table. Can you be more specific and explain this with an example or a real time scenario?

Re: CheckSum

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

Inorder 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.....

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 ve to run the checktbl utility in level 3 so that it will diagnos the entire rows,byte by byte...

Re: CheckSum

This info regarding checksum is very useful. I have some questions in this regard.

In case of dik errors what will happen to the table?                                                                                    Will the table be created by correcting the disk errors or table won't be created?                                      And what do we mean by data corrupted?  Does it mean like data stored in wrong format?  

Can anyone provide info for this.