Notes

The model can either be set up to allow concurrent *DSNRs and *PGMRs/*USERs into the model by setting the model value YOPNACC to *YES, or the model value can be left as *NO where either a single *DNSR or multiple *PGMRs/*USERs can be in the model concurrently.
To add and remove permanent locks, or to change the Open Access (YOPNACC), you must have all rights to the data model. (Designer with locks capability).
To edit a model as a user of type *DSNR, you must have at least all rights except for existence to the model. Generally the most convenient way to arrange this is to grant all rights to all the objects in the model library (the default), and then to control access to the model by granting or revoking rights to use the data area YMDLLIBRFA in the model library. The YEDTMDL command checks the user's authority to this data area before allowing entry to the model.
For example, to revoke all rights to user profile IVAN to edit or view a model MYMDL:

RVKOBJAUT OBJ(MYMDL/YMDLLIBRFA) + OBJTYPE(*DTAARA) USER (IVAN) AUT(*ALL)

Or to grant user profile IVAN rights to an edit model MYMDL as designer with lock capability:

GRTOBJAUT OBJ(MYMDL/YMDLLIBRFA) + OBJTYPE(*DTAARA) USER(IVAN) AUT(*ALL)

To override the model value YOPNACC (represented in the command by OPNACC) by specifying *NO, you must have all rights to the data area YOPNACCRFA. Access rights to YOPNACCRFA can be assigned or revoked in the same way as above.
Should you wish to change the YOPNACC value temporarily just for the duration of the session, you must synchronize the model on exit.