Hi Ningappa,
As term suggest Archive routing helps to route the archive files to a particular content repository.
Case 1: If your customer is maintaining the content repositories based on different retention years(10/8/6 years), you can maintain the conditions under customizing to route the archive files to specific repository.
Case 2: If customer is maintaining the country specific content repositories, then archive files created particular to that country(company code/sales org or plants) can get route to that repository.
Note : If the archive routing is maintained, input gave under write report has to meet the condition, otherwise write job will get fail.
Regards,
Sudheer T