Extending Master Data: Message RSAR508

I've previously avoided extending SAP master data but am experimenting with adding an attribute to cost center master, which I intended to fill in the transfer rules. When I try to access the transfer rules I receive the message below.

Can anyone explain what the message means? In particular what does "Define the PSA in the source system" mean?

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Transfer method 'TRFC with PSA' is not supported by the source system

Message no. RSAR508

Diagnosis

The PSA transfer method is used to transfer data from source system DR3CLNT310 to transfer structure 0COSTCENTER_ATTR_DD. Source system DR3CLNT310 does not support a PSA transfer.

Procedure

Define the PSA in the source system.