Dear Darshan
your understanding might be not"100%" correct
1.) if you have e.g. data in property density the "values" maintained (and more) does all have the same "usage". So not the "characteristic" does have the usage, but the "whole data record" does have the usage
So your sentence might be "misleading"
"Just to elaborate I will take an example there is a characteristics SAP_EHS_XXXX_YYY_REMARKS earlier under usage the following details were maintained Rating - PUBLIC, Validity area category - REGION and Validity area - GB but now the requirement is characteristics should be available for Validity area - REG_WORLD instead of GB. "
=> not the "characteristic" does have usage; the data record as such does have the usage
2.) you mix"maintenace" topics and " wwi layout" topics
If your data record does have "PUBLIC/GB" and now (because of whatsoever reason) it should have PUBLIC / REG_WORLD just change the validity area..
This is, in your case, a topic of "massupdate" (if i understand your whole requirement); and there is no option to do so, The "only" chance is by using EHS export and then EHS import (I can not recommend this in live system)
3.) to look at generation variant is the "last" chance to solve demands and here the special handling of "validity areas" in gen variants comes in place
PLease read here: WWI for Beginners;
The handling of "usage" in WWI reports (and gen variants) is explained there (and you will find good documentation in SAP online help)
IN your case you are (by whatsover reason) in a "bad" starting position as you need to get updates for the values in 10.000 specs....
Before you do that: think twice: is it a good idea to change "usage"? There are lot of subsequent process whcih could be triggered (potentially) if you do mass updates (list is quite long)
If there is the need to have "similar" updates in the future you should look for a long term solution and not on "short term"
If you have the need to execute "similar" tasks in future in most cases a "secondary data determination approach" is a good option (CUSTOMER SPECIFIC IMPLEMENTATION !(
Therefore check: Customer Exits in SAP EHS MANAGEMENT
May be check as well this: Massive Identifier change/creation for Substance.
There is always a solution (that is the good news); the "bad" one: it is in most cases 100% own development
C.B.