Configuring VTAM for DRDA via SNU/LU 6.2
To enable DB2 to communicate using the DRDA datastream via APPC SNA/LU 6.2, several DDF VTAM parameters must be configured.
1. Define the DB2 system LU Name to DB2/390/MVS BSDS (bootstrap data set).
The APPC logical unit which DDF uses to manage APPC SNA/LU 6.2 connections can be defined via the DSNTINST TSO CLIST; refer to the DB2 Network LUNAME prompt (option 37).
At startup, DDF reads the LU name defined in the DB2 BSDS and prepends the unique system VTAM net ID to form a fully qualified netid.luname, which is used to manage APPC LU 6.2 conversations (connections) between DRDA clients and the target database instance.
2. Define the VTAM APPLID.
The LUNAME defined in the DB2 BSDS must correspond to a VTAM APPLID; a sample VTAM macro definition for the LU name LU1 appears below:

DB2 APPL | VBUILD TYPE = APPL
LU1 | APPL APPC = YES
| AUTH = (ACQ)
| AUTOSES = 1,
| DSESLIM = 20,
| DMINWNL = 10,
| DMINWNR = 10,
| SECACPT = ALREADYV,
| EAS = 509,
| MODETAB = DB2MODES
| PARSESS = YES,
| SRBEXIT = YES,
| VPACING = 2

The important parameters above are the APPL ID = LU1, which must match the value of the LU name entered in the DB2 BSDS. In addition, setting SECACPT = ALREADYV provides for maximum flexibility when validating DB2 userid/password security at connect time. When SECAPT=ALREADYV is configured, the following connection options are available.

APPC Security | CONNX Option | Values sent from client to host
Same | UserID | UserID only
Program | UserID & Password | User ID and password
None | None | None, but DB2 for OS/390 and MVS reject this option

3. Define the VTAM Mode Name (IBMRDB).
The VTAM APPLID definition above references a VTAM mode table = DB2Modes. Within this mode table, you must define mode name IBMRDB or a custom mode name. The IBMRDB mode name is the IBM-recommended default for managing DRDA datastream traffic via APPC LU 6.2.

IBMRDB |  |
MODEENT | LOGMODE=IBMRDB, | DRDA DEFAULT MODE
| TYPE = 1, | NEGOTIABLE BIND
| PSNDPAC=X’00’, | PRIMARY SEND PACING COUNT
| SSNDPAC=X’02’, | SECONDARY SEND PACING COUNT
| SRCVPAC=X’00’, | SECONDARD RECEIVE PACING COUNT
| RUSIZES=X’8989’, | RUSIZES IN –4K OUT-4K
| FMPROF=X’13’, | LU6.2 FM PROFILE
| TSPROF=X’07’, | LU6.2 TS PROFILE
| PRIPROT=X’BO’, | LU6.2 PRIMARY PROTOCOLS
| SECPROT=X’BO’, | LU6.2 SECONDARY PROTOCOLS
| COMPROT=X’50A5’, | LU6.2 COMMON PROTOCOLS
| PSERVIC=X’060200000000000000102F00’, | LU6.2 LU TYPE
APPNCOX=#CONNECT |  |