Sharing the same metadata can cause issues, for heterogeneous sources or when attempting to use multi-source for multiple schemas, as described below:

Teiid issues queries with the catalog and schema of the the primary source. This gives invalid results for all the other sources.

If the non-primary source connection(s) have authority to access the primary's catalog/schema then duplicated rows are returned to the client.

If it does not have authority then an error results.

Note: In MySQL this effect can be mitigated by setting useCatalogName=false. This seems to be because the JDBC4DatabaseMetaData.getTables() method does not return a schema; so suppressing the catalog is enough.

For the System-I whose equivalent getTables() method returns a catalog and schema, I couldn't find a workaround.