DB2 SQL, SYSCAT, SYSIBM, etc

We have some SQL that runs a query via JDBC such as:

SELECT TABNAME FROM SYSCAT.TABLES WHERE TABSCHEMA = ? AND TYPE = ? ORDER BY
TABNAME

The ? marks are replaced before running it.

This works on other DB2s but does not appear to work on iSeries V5R2.

After searching the midrange-l archives, V5R2 info center, and newsgroups, I
am still confused. I see some things that imply that SYSCAT.TABLES should
work on iSeries, but others that imply that (at least) syntax changes will
be necessary, such as: 

SYSCAT -> SYSIBM
TABNAME -> TABLE_NAME
TABSCHEMA -> TABLE_SCHEMA

Am I understanding this correctly? Is there an easier way? If we change the
query syntax for iSeries, will there still be other subtle differences that
will cause problems?

THANKS in advance!
-Marty