You are running Graphical Data Display Manager (GDDM) V3.2 and are looking for information on changing ADMDATRN to support Arabic.
Resolving the problem
See section 188.8.131.52 "Altering ADMDATRN to support the Arabic character set" in the GDDM System Customization and Administration guide. This section can be used to make the changes needed to ADMDATRN. Attached below is a converted ADMDATRN for Arabic support.
Note: Code page 420 is not a supported code page, so you can not set the Application Code page to 420. You should leave the application code page set to the default ADMMDFT APPCPG=351. This should have no effect on the characters displayed at the terminal. There is no GDDM fix to suppress the DSQ10344 message as this is issued by QMF. The message is a warning that the codepage of DB2 differs from that of GDDM and that incorrect characters might be displayed. However the altered ADMDATRN addresses that issue and ensures that the right data is displayed.