yaz_schema specifies the schema for retrieval.
This function should be called before yaz_search or yaz_present.
The connection resource returned by yaz_connect.
Must be specified as an OID (Object Identifier) in a raw dot-notation (like 1.2.840.10003.13.4) or as one of the known registered schemas: GILS-schema, Holdings, Zthes, ...
No value is returned.