Moving attachments between 2 SM instances

Hi Experts,

I have a requirement to move ( only update) location table records between 2 instances. All records in 1 instances exist in the other instance, but source system consist of alot of custom fields / information related to the location and this needs to be made available on the target system.

I am using HP Connect-IT to do this. I am able to update the existing location records on the target instances, but unable to move the attachments. 

I tried mapping the attachment collection between source and target documents types, but this hasnt helped.

Any guidance.