Per the DDM manual , pg 52 for ACCSEC.
The normal response to the ACCSEC command is
ACCSECRD (SECMEC (value
"if the target server supports the SECMEC value requested by the source server, then a single value is returned for SECMEC and is identical to the secmec value send in the ACCSEC command.
but if the target server does not support the secmec requested by the source server, then only one or more values in SECMEC are returned. "
Currently in the network server, if the security mechanism is not supported, 3 SECMECs are sent with the supported security mechanisms.
see : DRDAConnThread.writeACCSECRD.
This needs to be changed to send one SECMEC with a list of secmec values.