Hi,
For such kind of errors you can try to search oss notes on http://service.sap.com/notes with the name of the function module. And the following tricks will help you reduce the number of hits:
Tip n°3: how to improve OSS Notes search results
SAP Automated Note Search Tool: I'm loving it!
As far as I can see I_SCHEMA_NAME was introduced with OSS note 1732117 in SAP_BASIS 731. So maybe that's the note you were looking for... but without further information about your system patch level it's impossible to tell.
Hope that helps,
Nicolas.