When using DMLO, a new IDMS user receives error E2028 USER DOES NOT EXIST, TRY AGAIN. How to resolve this error?
One possibility for the E2028 error is the DMLO userid is not a valid userid. Another possibility is that the DMLO Userid is not defined in IDD. If that's the case you need to add this DMLO userid to IDD for the dictionary that accessing DMLO. DMLO does not use central security and thus an IDMS Userid and DMLO Userid are not identical.
DMLO uses IDD security instead of central security, therefore the DMLO security program DBMSDMLO requires a USER-047 record in the IDMSNWKA subschema to validate dictionary security via IDD.
CA IDMS Database DML Online Option User Guide, 5.2.1 Severity Codes
CA-IDMS Installation and maintenance- z/OS and OS/390, Appendix G.1.1 Advantage CA-IDMS DMLO Security