SQLCODE -518

The reason mentioned in the DB2 manual for SQLCODE -518 is "THE EXECUTE STATEMENT DOES NOT IDENTIFY A VALID PREPARED STATEMENT"

You may get this SQLCODE for many reasons. I don't know them all. For me this is what happened. When I tried to connect to a remote DB2 database (on LUW) from a COBOL program on the mainframe, the CONNECT was successful. However when I tried to run an SQL on that database I got this SQLCODE.

After researching for a while, I found that I had an existing SQL statement within EXEC SQL and END-EXEC. That worked good. But when I commented out one of WHERE clause statements (using * at column 7), it gave me this error. I moved the commented statement to the line after END-EXEC and it started working again.

Bottom line is DB2 doesn't like COBOL-like commented code inside EXEC SQL and END-EXEC when you are trying to run the SQL at a remote DB2 database.

Copy Data from DB2 for z/OS to DB2 for LUW (UDB)

One of the applications developer in our shop wanted to know if he can copy data from a mainframe DB2 table to DB2 UDB on LUW. Though there are several ways of doing it, this is the one suggested him assuming the table structure in z/OS and LUW are the same.

1. Some of the tools that can be used to achieve this: Quest Central for DB2, Toad for DB2 or DB2CMD interface

2. Connect to the mainframe database (CONNECT TO ssid) and issue the EXPORT command "EXPORT TO d:\file_name.ixf OF IXF MESSAGES d:\msg_export.txt SELECT *FROM prefix.table_name"
Note: Don't forget to check the message file before moving onto the next step

3. Connect to the LUW database and issue the IMPORT command
"IMPORT FROM d:\file_name.ixf OF IXF MESSAGES d:\msg_import.txt INSERT INTO prefix.table_name"
Note: Don't forget to check the message file

It's that simple. But remember that this works well for relatively smaller tables. For larger tables, you may have to use the LOAD command with proper COMMIT COUNT.

How to query tables from different DBMSs?

There are times when you need to query tables from different Database Management Systems (DBMSs). For example, one type of information or data may reside in DB2 UDB table and another in DB2 for z/OS or even Oracle table. How will you write queries that joins these tables and fetches the desired results?

The answer is 'federation'. If you have DB2 UDB, and want to join a table from Oracle or DB2 for z/OS, create a federated table image of the table that resides in the other DBMS. Once you create a federated table, you can write queries treating it like a table that resides on the local DB2 UDB server.

For example:
SELECT L.col1, L.col2, F.cola, F.colb
FROM Local_Table L, Federated_Table F
WHERE L.col3 = F.colc

Remember that for "federation" to work, you need DB2 Connect or a similar product.

You can find more details here:
IBM Federated Database Technology