Hii Uday,
1)what are change pointers
Ans : . Normally Change pointer created when we do create/change in transaction data in APO. then we need to process those change pointers to ECC.
2) why should we process the change pointers during CCR , why not push to R/3 directly instead of process change pointers. If we push what would be the result.
ANS: No need to run CCR every time. You can schedule some EOD jobs for processing change pointers (/sapapo/c5.).
CCR need to run when there is inconstancy occurs .
There are global setting (configuration), where you can put how to process change pointer(which application/Order type). Depends on it change pointers created, Otherwise it'll not create an pointers, it'll directly move to APO.
Go through the SAP Help http://help.sap.com/saphelp_scm50/helpdata/en/3d/d977377fae0261e10000009b38f842/content.htm
APO application is based SCM number range , when it moves to ECC it picks the ECC number range which is the valid one.
Sometimes some client don't want to move orders to ECC directly , They want to review the planning , then they make certain changes if required or if the planning is not as expected, they will simply delete the change pointers. And cancel the planning.
It depend on customer to customer how they want to do their process..
Regards
Debashis