DB2400Dialect.getIdentitySelectString() fails when naming=system since it returns:
"select identity_val_local() from sysibm.sysdummy1"

it should return:
"select identity_val_local() from sysdummy1"

Error:
When using DB2400Dialect with naming=system, the following error
something like this will be generated in log:
SQL5016] Qualified object name SYSDUMMY1 not valid

Explanation:
On db2 on as/400, table names in sql can be fully qualified with schema name or unqaulified but they can't be mixed.

Qualified naming example:
When "naming" jdbc property is configured as:
jdbc:db2://someserver;naming=sql

then tables must be qualified with schema name:
select * from schema1.mytable

Unqualified naming example:
When "naming" and "library" jdbc properties are configured as:
jdbc:db2://someserver;naming=system;libraries=schema1,schema2,sysibm

then tables must NOT be qualified with schema name:
select * from mytable

mytable will be searched for in schema1 then schema2 then sysibm.

Solution:
The solution would be to allow DB2400Dialect to know when naming=system, then to omit "sysibm." qualification in sql.

See:
http://publib.boulder.ibm.com/infocente ... operty.htm
http://publib.boulder.ibm.com/infocente ... /rzahh.pdf (page 313)