SQKL: Puzzle using new keyword value *AUTO

In coding a service procedure as a sort-of I/O server.

I have defined a data structure to receive rows from an SQL View:

DCL-DS   MX  EXTNAME( MYSQLVIEW )  DIM(*AUTO:9999) ;

..where

This exact syntax works perfectly elsewhere without the *AUTO.

I'm getting error SQL5011  Host structure array MX not defined or not usable for reason code 1.

Reason code 1: Host structure array not defined or is not a valid structure. A valid structure must have at least one valid member....

Can somebody help or point me somewhere. I saw something similar before so I suspect it's not the *AUTO throwing things off.

-Alan Cassidy