Communication link parameters

BARR/RJE

On the Communication Link tab you can specify the BARR/RJE communication protocol and physical attachment between the host system and remote computer. This topic describes the VTAM and NCP parameters you must specify in the BARR/RJE software for the communication link. These parameters must match those specified in the host VTAM and NCP parameter libraries. Your host programmer can provide the correct values to enter into the BARR/RJE software. VTAM is the mainframe program for the SNA communication protocol. NCP is the program that resides in the mainframe communications controllers.

When you finish configuring the communication links on the Communication Link tab, click NCP and Physical Unit to view sample statements the host programmer needs to enter in the host VTAM and NCP parameter libraries. The host programmer must set certain host parameters for BARR/RJE to operate. An existing remote definition used for other RJE equipment might not work with BARR/RJE. You will save time and effort getting your system running if you adhere to the recommended host definition. You can print these screens for the host programmer by clicking Print on the NCP or Physical Unit dialog box.

NCP definitions are available for 802.2 LLC2 and SDLC connections. Physical unit (VTAM) definitions are only available for 802.2 LLC2, HPR/IP, and SDLC switched connections.

What do you want to do?

SDLC switched line connections

On SDLC switched (dial) lines, host modems automatically answer remote user phone calls as shown in the following graphic. The modems use the public phone system at speeds from 1,200 to 56,000 bps.

SDLC Switched Line Connections

SDLC dial lines use modems to answer remote phone calls.

The BARR/SNA SDLC Link Service configuration utility and the SDLC Connection Configuration dialog box are used to configure the SDLC link service for the BARR/RJE software. The parameters specified are also used by VTAM and NCP on the mainframe. Your host programmer can provide you with the correct parameter values. After you enter the communication link parameters in the software, BARR/RJE produces samples of the statements the host programmer needs to enter in the host VTAM and NCP parameter libraries. You can view and print these statements by clicking NCP and Physical Unit on the Communication Link tab.

NCP definition for an SDLC switched line

The following is the recommended NCP definition for an SDLC switched line. You can access this dialog box by clicking NCP on the Communication Link tab. The parameters that appear in the dialog box vary depending on the settings configured in the BARR/RJE software. The parameters that change are displayed in blue text.

NCP Definition for Switched Line Dialog Box

GROUP macro

The GROUP macro instruction gives common parameter settings for all LINE macros in the group.

group

GROUP DIAL=Yes,LNCTL=SDLC

Required parameters

Parameter	Description
group	Optional macro label.
DIAL=Yes	Indicates this is a dial-up line.
LNCTL=SDLC	Indicates the line control is SDLC.

LINE macro

The LINE macro defines the line at the host and is necessary for SDLC connections.

linename LINE	ADDRESS=(aaa,FULL),DUPLEX=FULL,	X
	NRZI=Yes,RETRIES=(8,2,20),SPEED=nnnnnn,TRANSFR=16

Required parameters

Parameter	Description
linename	The VTAM name of the communications line.
ADDRESS=	Line interface address. (aaa,FULL) – Indicates the line interface address, aaa, when you specify DATMODE=FULL. aaa – Indicates the line interface address, aaa, when you specify DATMODE=HALF.
DUPLEX=FULL	The line and modem can send and receive data simultaneously.
NRZI=YES\|NO	NRZI is a method to encode binary data over a serial interface. Check if your host uses NRZI encoding. YES – Use NRZI encoding. Use this option if frequent SDLC aborts occur. NO – Do not use NRZI encoding.
RETRIES=(m,t,n)	The number of attempts the system will make to recover from communications errors. m – Maximum retransmissions of a frame while waiting for a normal response. The recommended value is 8. t – Time in seconds paused after m retransmissions have failed. The recommended value is 2. n – Number of times the above error recovery sequence is repeated. The recommended value is 20.
SPEED=nnnnnn	Required. Because the modem provides the bits-per-second clock, this parameter does not affect BARR/RJE functions, but the IBM Network Performance Monitor uses this value to calculate statistics.
TRANSFR=16	The number of NCP buffers. This value corresponds to the maximum amount of data (the data transfer limit) that NCP will receive from the line during a single data transfer operation.

System default values

Parameter	Description
CHECK=NODCD	The Data Carrier Detect (DCD) line from the modem will not be monitored.
CLOCKNG=EXT	External clocking indicates that the modem’s clock will control the transmission rate.

PU macro

The PU macro names and describes a PU. At log on, the PU macro in the NCP definition is replaced with the PU macro from VTAM.

puname

MAXLU=5

Required parameters

Parameter	Description
puname	The PU’s name conforms to the naming convention at your site. The VTAM operator uses the name to vary the unit active or inactive and to query the unit’s status.
MAXLU=n	The maximum number of LUs used with this line. Use the LU macro formula to calculate the number of LUs you need. If you are upgrading from DOS-based BARR/RJE, the number of Non-RJE LUs specified on the Communication Link tab is also included in the calculation.

Physical Unit definition for SDLC switched line

PU Definition for Switched Line Dialog Box

PU macro

The PU macro names and describes a physical unit.

puname	PU	ADDR=C1,	X
		IDBLK=03D,DATMODE=FULL,	X
		IDNUM=12345,	X
		MAXDATA=1033,MAXOUT=7,	X
		PACING=7,PASSLIM=7,VPACING=7

Required parameters

Parameter	Description
puname	The PU’s name conforms to the naming convention at your site. The VTAM operator uses the name to vary the unit active or inactive and to query the unit’s status.
ADDR=C1	The 8-bit address used by SDLC. This address, the first byte of every frame, separates messages sent to different PUs on the same line.
DATMODE=FULL\|HALF	Specify whether the PU data mode is full duplex or half duplex. FULL – Default. The system sends and receives data simultaneously resulting in twice the throughput. The V.32 modem standard supports full duplex on dial-up lines. Some modems do not support full-duplex communications. If you select DATMODE=FULL on the BARR/SNA SDLC Link Service Link tab, the host programmer must also specify it at the host. If the computer and host settings do not match, the software might have communication problems such as timeouts or lowered performance when it sends data to the host. HALF – In half duplex, the communications line is in either a send or receive mode so less than half the capacity of the line is available for use. To maximize performance, select DATMODE=FULL on the SDLC Connection Configuration dialog box and in the VTAM PU definition. You can achieve maximum BARR/RJE performance with full-duplex mode. Full duplex enables you to send and receive data simultaneously, often doubling throughput. You can even improve one-way throughput because you can receive acknowledgments while you send data.
IDBLK=bbb IDNUM=nnnnn	Use these parameters to identify the remote’s PU definition. During Xid negotiation, the remote sends an Exchange ID that contains the IDBLK and IDNUM parameters. VTAM searches for the PU identified by IDBLK and IDNUM and uses this PU for the rest of the communications session.
MAXDATA=265\|521\|1033\|2057	The maximum amount of data you can send on the PU in one frame. This value includes nine bytes of header information plus the data length. The default value is 1033. To maximize performance, you can increase throughput by sending larger frames of data. Send 1024 bytes by setting MAXDATA to 1033 on the SDLC Connection Configuration dialog box and the VTAM PU definition. This step reduces the amount of control information and total number of frames sent. Setting MAXDATA to 2057 can result in greater system throughput, but it is not recommended for Ethernet or other LAN equipment that will not support the larger packet size.
MAXOUT=7	Specifies that up to 7 frames of information will be sent before pausing for a response. The maximum MAXOUT value of 7 results in the highest throughput.
PACING=n	Determines how much data gets sent to BARR/RJE before the system needs a pacing response to send more data. Pacing is a flow-control mechanism that prevents the host from sending data faster than BARR/RJE can print or otherwise handle it. Values smaller than 7 often lower performance. This parameter overrides the SRCVPAC value in the LOGMODE.
PASSLIM=n	The maximum number of information frames sent to the PU at one time. This parameter is usually set to the same value as MAXOUT.
VPACING=n	Similar to the PACING parameter, but VPACING determines pacing between the RJE system and VTAM. Values less than 7 lower efficiency. To maximize performance, setting parameters to larger values can improve BARR/RJE performance. If PACING=7 and VPACING=7 in the VTAM PU definition, the host can send seven data frames before it requires a pacing response. On a half-duplex line, the host sends 7 frames at a time. When you specify PACING=7, the pacing response could be returned in time for 7 more frames of data to be sent. Include MAXOUT=7 in the PU definition.

System default values

Parameter	Description
DISCNT=(NO)	Do not disconnect the PU until BARR/RJE requests it.
ISTATUS=ACTIVE	The PU will be activated automatically.
PUTYPE=2	BARR/RJE uses the Physical Unit Type 2 protocol.

Other parameters

Parameter	Description
DLOGMOD=nnnnnnnn	Specify the logon mode table entry to use by default.
MODETAB=nnnnnnnn	Specify the mode table containing the logmode entries. ISTINCLM is the default IBM-supplied mode table usually present with VTAM.
SSCPFM=USSSCS	If this parameter is set, then the host's logon type and the Logon type selected on the RJE Description tab, must be configured as Character Coded. The system default is SSCPFM=FSS, which indicates that the Logon type must be Formatted.

LU macro

The LU macro instructions define logical units allocated to the RJE devices.

luname02 LU

LOCADDR=2,

** RJE LU

Use the LU macro formula to calculate the number of LUs you need.

Required parameters

Parameter	Description
lunamenn	The LU name conforms to the naming convention at your site. BARR/RJE does not use this name.
LOCADDR=i	The local addresses must be unique. The maximum value for i is 20 when you use Barr software. MVS/JES2 supports a maximum of 13 LUs with BARR/RJE.
BATCH=YES	Indicates the processing priority. Batch applications, such as RJE, require low priority. While interactive applications, such as 3270 terminal sessions, usually have higher priority. For VTAM Version 4, Release 3 or later, replace this parameter with the Class of Service (COS) parameter in the LOGMODE for the host application.

SDLC nonswitched (leased) line connection

Dedicated point-to-point lines operate at speeds from 4,800 to 2,048,000 bps. You can lease dedicated lines from a phone company or install them in a single building or business. You can use either a modem or DSU/CSU, depending on whether the dedicated line is analog or digital.

SDLC Nonswitched (Leased) Line Connection

SDLC leased lines use modems or DSU/CSUs to answer remote phone calls.

The BARR/SNA SDLC Link Service configuration utility and the SDLC Connection Configuration dialog box are used to configure the SDLC link service for the BARR/RJE software. The parameters specified are also used by NCP on the mainframe. Your host programmer can provide you with the correct parameter values. After you enter the communication link parameters in the software, BARR/RJE produces a sample of the statement the host programmer needs to enter in the host NCP parameter library. You can view and print this statement by clicking NCP on the Communication Link tab.