HP OpenVMS Systems Documentation

HP OpenVMS System Management Utilities Reference Manual

SET VC

Sets values for the virtual circuit management parameters (checksumming, compression, ECS delay threshold, transmit window size, and receive window size values).

Format

SET VC nodename

Parameter

nodename[,...]
Includes VCs to specific nodes, which you can use wildcards to specify.
Use the /EXCLUDE qualifier to exclude VCs to specific nodes.
Use the SHOW CHANNEL or SHOW VC command to display VC names, which are simply the names of remote nodes.

Qualifiers

/CHECKSUMMING

/NOCHECKSUMMING
Enables or disables checksum verification on the selected VCs to the specified nodes.
You can use this command alone or in combination with the system parameter NISCS_PORT_SERV. (For more information, see online help for NISCS_PORT_SERV.)
Note that the the SET VC/CHECKSUMMING setting is not valid beyond the life of the system. Therefore, you might want to include SET VC/CHECKSUMMING commands in your startup file, or reissue these commands at the next boot.
/COMPRESSION

/NOCOMPRESSION
Enables or disables sending compressed data by the specified VCs. The default is /NOCOMPRESSION.
Usage notes:

Compression is used only if the partner node has a PEdriver version that supports it.
You can also enable the use of compression with the NISCS_PORT_SERV system parameter. For more information about NISCS_PORT_SERV, see the System Parameter appendix in this manual.
The /NOCOMPRESSION qualifier does not override compression enabled by setting bit 2 of NISCS_PORT_SERV.

/ECS_MAX_DELAY=n

/NOECS_MAX_DELAY
Sets a management-specified lower bound on the maximum delay (in microseconds) an ECS member channel can have. The value for n can be any value between 0 and 3000000. /NOECS_MAX_DELAY disables a prior management delay setting.
You can use this command to override the PEdriver automatically calculated delay thresholds to ensure that all channels with delays less than the value supplied for n are included in the VC's ECS.
The command operates as follows: Whenever at least one tight peer channel has a delay of less than the management-supplied value, all tight peer channels with delays less than the management-supplied value are automatically included in the ECS. When all tight peer channels have delays equal to or greater than the management setting, the ECS membership delay thresholds are automatically calculated and used. The /NOECS_MAX_DELAY qualifier disables management control by setting the management delay value to zero.
You must determine an appropriate value for your configuration by experimentation. An initial value of 2000 (2 ms) to 5000 (5 ms) is suggested.

CAUTION
By overriding the automatic delay calculations, you can include a channel in the ECS whose average delay is consistently greater than 1.5 to 2 times the average delay of the fastest channels. When this occurs, the overall VC throughput becomes the speed of the slowest ECS member channel.
An extreme example is when the management delay permits a 10 Mb/s Ethernet channel to be included with multiple 1 Gb/s channels. The resultant VC throughput drops to 10 Mb/s.

Note that the SET VC/ECS_MAX_DELAY setting is not valid beyond the life of the system. Therefore, you might want to include SET VC/ECS_MAX_DELAY commands in your startup file or reissue these commands at the next boot.
/EXCLUDE=(nodename[,...])
Excludes VCs to specific nodes, which you can use wildcards to specify.
/WINDOW=RECEIVE=n

/WINDOW=NORECEIVE
Sets a management-specified upper bound on the receive window size (that is, the number of out-of-order packets this VC holds in its resequencing cache while awaiting the next in-order packet or packets).
You can use this qualifier to override the automatically calculated receive window size. This ensures that the VC has enough buffering to receive the expected maximum number of out-of-order packets.
Usage notes:
The window size value n must be an exact power of 2.
Never use settings that cause the receive window of a VC to be smaller than the transmit window of the partner node. Otherwise, the partner can send packets that cannot be cached when a packet is lost. This results in unnecessary retransmissions, and might cause channels not to be used because they become "lossy." This leads to the remaining restrictions listed.
Always decrease the transmit window size of a VC's partner node before decreasing a VC's receive window size.
HP recommends using SYSMAN to decrease both the local and the remote VC transmit window sizes before increasing the local and remote receive window sizes (as shown in the example).
Always increase the receive window size of a VC's partner node before increasing a VC's transmit window size.
HP recommends using SYSMAN to increase both the local and the remote VC receive window sizes before increasing the local and remote transmit window sizes.
Whenever you enter the SET VC/WINDOW=RECEIVE command, the following sequence of events occurs:
The VC's current resequencing cache is emptied.
The VC partner node automatically retransmits any discarded packets.
As a result of 2, the VC and channel retransmit counts increase.
A few messages similar to the following might be displayed, indicating that one or more channels has temporarily become "lossy":
%PEA0, Excessive packet losses on LAN Path from EWA to EWC on REMOTE NODE STAR
The partner node recovers automatically within a few seconds.
You can use the SCACP> CALCULATE WINDOW_SIZE command to assist you in selecting the size to use for transmit and receive windows.
/WINDOW=TRANSMIT=n

/WINDOW=NOTRANSMIT
Sets a management-specified upper bound on the transmit window size (that is, the number of out-of-order packets this VC sends while awaiting acknowledgment of the transmitted packets) to n. The /WINDOW=NOTRANSMIT qualifier resumes automatic control of the window size and changes the management transmit window size to zero.
You can use the /WINDOW=TRANSMIT qualifier to override the automatically calculated transmit window size to ensure that the VC has enough buffering to receive the expected maximum number of out-of-order packets.
Usage notes:

The window size value n must be an exact power of 2.
Never use settings that cause the receive window of a VC to be smaller than the transmit window of the partner node. Otherwise, the partner can send packets that cannot be cached when a packet is lost. This results in unnecessary retransmissions, and might cause channels not to be used because they become "lossy". This leads to the following restrictions.
Always decrease the transmit window size of a VC's partner node before decreasing a VC's receive window size.
HP recommends using SYSMAN to decrease both the local and the remote VC transmit window sizes before increasing the local and remote receive window sizes.
Always increase the receive window size of a VC's partner node before increasing a VC's transmit window size.
HP recommends using SYSMAN to increase both the local and the remote VC receive window sizes before increasing the local and remote transmit window sizes (as shown in the example).
You can use the SCACP CALCULATE WINDOW_SIZE command to assist you in selecting the size to be used for transmit and receive windows.

Examples

 $RUN SYS$SYSTEM:SYSMAN
SYSMAN> SET ENV/NODE=LARRY
 DO MC SCACP SET VC LARRY/WINDOW=TRANSMIT=16
 SET ENV/NODE=CURLY
 DO MC SCACP SET VC CURLY/WINDOW=TRANSMIT=16
 SET ENV/NODE=LARRY
 DO MC SCACP SET VC LARRY/WINDOW=RECEIVE=16
 SET ENV/NODE=CURLY
 DO MC SCACP SET VC CURLY/WINDOW=RECEIVE=16
 EXIT

This example shows how to decrease window size. The transmit and receive window sizes are 32 on both nodes, and the commands decrease the window size for the VC between LARRY and CURLY. (You can enter the commands on either node.)

 $RUN SYS$SYSTEM:SYSMAN
SYSMAN> SET ENV/NODE=LARRY
 DO MC SCACP SET VC LARRY/WINDOW=RECEIVE=64
 SET ENV/NODE=CURLY
 DO MC SCACP SET VC CURLY/WINDOW=RECEIVE=64
 SET ENV/NODE=LARRY
 DO MC SCACP SET VC LARRY/WINDOW=TRANSMIT=64
 SET ENV/NODE=CURLY
 DO MC SCACP SET VC CURLY/WINDOW=TRANSMIT=64
 EXIT

This example shows how to increase window size. The transmit and receive window sizes are 32 on both nodes, and the commands increase the window size for the VC between LARRY and CURLY. (You can enter the commands on either node.)

SHOW CHANNEL

Displays PEdriver channel information for specific nodes. Each channel is a single NISCA communications path between a LAN device on a local system and a LAN device on a remote system.
Use the SHOW CHANNEL command to display node names and local and remote device names.

Format

SHOW CHANNEL nodename

Parameter

nodename[,...]
Includes channels to specific nodes, which you can use wildcards to specify. Each node name can be accompanied by optional qualifiers to specify local and remote device names. If no local or remote device name is specified, all channels associated with the specified node name are included.

Qualifiers

/ALL
Includes all channel data.
/COUNTERS
Includes channel counters data.
/ECS

/NOECS
Includes only channels that are (or are not) members of the ECS.
/EXCLUDE=(nodename[,...])
Excludes channels to specific nodes, which you can use wildcards to specify. Each node name can be accompanied by optional qualifiers to specify local and remote device names. If no local or remote device name is specified, all channels associated with the specified node are included.
/INTERVAL
For the /COUNTERS display, displays the changes to counters since the last SHOW command.
/IP
Includes the IP channel data.
/LAN
Includes the LAN channel data.
/LOCAL_DEVICE=(landevicename/IPinterfacename[,...])
Includes specific LAN devices that identify the local end of the channel; you can use wildcards to specify LAN devices.
Use the SHOW LAN_DEVICE command to display device names.
/n
Displays the nth page. To select a particular page of a multipage display, specify the number of the page you want to display.
/OUTPUT=filespec
Creates the specified file and directs output to it.
/REMOTE_DEVICE=(landevicename/IPinterfacename[,...])
Includes specific LAN devices/IP interfaces that identify the remote end of the channel; you can use wildcards to specify LAN devices/IP interfaces.
Use the SHOW LAN_DEVICE command to display device names.
/SDA
Includes channel data displayed in SDA format, with all the data collected in one display for one channel.
/SUMMARY
Includes channel summary data. This is the default if /ALL, /COUNTERS, and /SDA qualifiers are not specified.

Examples

#1
SCACP> SHOW CHANNEL NODE20/LOCAL=EWA

The command in this example displays channel definition data for all nodes defined with local device EWA and any remote device and remote node name starting with NODE20.

#2
SCACP> SHOW CHANNEL/COUNTERS/INTERVAL SCACP> SPAWN WAIT 0:0:10 SCACP> SHOW CHANNEL/COUNTERS/INTERVAL

The first command in this example displays channel counters since the last SHOW command. The SPAWN command tells the DCL WAIT command to insert a 10-second delay. The second SHOW CHANNEL command displays counters after the 10-second period.

#3
SCACP> SHOW CHANNEL/1/3

The command in this example displays the first and third pages of data for all channels. The first page contains Channel Summary data, and the third page contains Channel Equivalent Channel Set (ECS) data.

#4
SCACP> SHOW CHANNEL/ALL

The following is a snapshot of the output for SHOW CHANNEL/ALL command.
Figure 21-1 Sample SHOW CHANNEL/ALL output

Table 21-2 describes the channel error data.

**Table 21-2 Channel Error Data**
Data	Description
Seq Retransmit	Number of times a sequenced VC packet sent on this channel was retransmitted, and the channel was penalized for the lost packet. Note that the sequential retransmit is not necessarily a reflection of lost packet. It is possible that there can be a PE which could have triggered a retransmitted and results in a duplicate packet to be sent. This is reflected in the number of duplicate packets received in the remote node. The XMIT:REXMT ratio is also a measure of for how many transmitted packet, a packet was retransmitted. A very low value (less than 1000) reflects a possible network congestion.
LAN Transmit Failures	Number of times the local LAN device reported a failure to transmit a packet, and channel was penalized for the lost packet.
Restart Channel	Close or restart because channel control packet received indicating that the other end closed the channel and is restarting the channel handshake.
Channel Init Timeouts	Channel initialization handshake timeout.
Listen Timeouts	No packets of any kind, including HELLOs, were received in LISTEN_TIMEOUT seconds.
Bad Authorization Msg	Received a Channel Control (CC) packet with a bad authorization field.
Bad ECO CC Msg	Received a CC packet with an incompatible NISCA protocol ECO rev. field value.
Bad Multicast Msg	Received a bad multicast CC packet.
CC Short Packet	Received a CC packet that was short.
CC Incompatible	Received a CC packet that was incompatible with existing channels for this virtual circuit.
Rcv Old Channel	Received a packet from an old instance of a channel.
No MSCP Server	No MSCP server available to respond to a received channel control solicit service packet asking this node to boot serve another node.
Disk Not Served	Disk is not served by this system.
Buffer Size Change	Change in buffer size.

#5
SCACP> SHOW CHANNEL/ECS

The following is a snapshot of the output for SHOW CHANNEL/ECS command.
Figure 21-2 Sample SHOW CHANNEL/ECS output

ECS State Channel ECS Membership Information

OpenVMS uses multiple interfaces to communicate with any other node in order to do load balancing of communication. However, at a given time not all interfaces that link the remote node are used to transmit datagrams. OpenVMS maintains a set of equivalent channels ECS (Equivalent Channel Set) within a VC. These channels have approximately equivalent transmission quality at a given time. Only the channels within the ECS are used to transmit datagrams to the given node. "A" is the generic format above may be "Y" (Yes) or "N" (No) stating whether the channel is in the ECS or not. The remaining characters specify the quality of the channel as they are derived from the channel performance data. The characters are:

A: T or L for Tight or Lossy
B: P, S, I, U for Peer, Superior, Inferior or Ungraded
C: F or S for Fast or Slow

For more details about ECS, see the section NISCA Transport Protocol Channel Selection and Congestion Control in the HP OpenVMS Cluster Systems manual.

Note

From OpenVMS Version 8.3 onwards, Topology change column from SHOW CHANNEL/FULL or /5 has been removed. This is because you must not consider this as an 'error' instead it is the count of failovers from one interconnect to the other interconnect. Whenever failover occurs to another interconnect the buffer size changes. Hence this topology change is counted under "Buffer SizeDecr" column in SHOW VC/FULL output.

You can view the IP channel data summary by using the /IPCHANNEL qualifier, for example:

$ SHOW CHANNEL <nodename>/IPCHANNEL

Figure 21-3 Sample SHOW CHANNEL/IP output

You can view the LAN channel data summary by using the /LANCHANNEL qualifier, for example:

$ SHOW CHANNEL/LANCHANNEL

Figure 21-4 Sample SHOW CHANNEL/LANCHANNEL output

SHOW CIRCUIT

Displays SCA circuit information. You can further qualify each node name you specify with additional parameters to uniquely identify a single circuit.

Format

SHOW CIRCUIT nodename

Parameter

nodename[,...]
Includes specific circuits to individual nodes, which you can use wildcards to specify.

Qualifiers

/EXCLUDE=(nodename[/PORT=portname[/RSTATION=n]][,...])
Allows you to exclude a specific circuit to a node. If multiple circuits to the same node exist, you can use the /PORT and /RSTATION qualifiers to uniquely identify the circuit.
/PORT=portname[/RSTATION=n]
If multiple circuits to the same node exist, you can use the /PORT and /RSTATION qualifiers to uniquely identify the circuit. You can use the /RSTATION qualifier only in conjunction with the /PORT qualifier.

Example


SCACP>SHOW CIRCUIT

The command in this example displays all circuits to nodes over port PEA0.

 
 Circuit data for CLUIO2 at 07-DEC 11:55:31.80 
 
  Node     Port   Priority   Load               Remote  Remote 
  Name     Name   Cur   Mgt  Class    State     Station  Type 
 -------- -------- ---- ---- -------- --------  -------  -------- 
 LYNX03   PEA0        0    0       10     Open      dc       NI 
 CLUIO1   PEA0        0    0       10     Open      dd       NI 
 PRMMC2   PEA0        0    0       10     Open      de       NI 
 RXBOT1   PIB0        5    0       48     Open       4     RF72 
 RXTOP1   PIB0        5    0       48     Open       1     RF73 
 RXTOP0   PIB0        5    0       48     Open       0     RF73 
 CLUIO1   PIB0        5    0       48     Open       7     N710 
 R4JC3I   PIC0        5    0       48     Open       7     RF73 
 R4HLEK   PIC0        5    0       48     Open       5     RF73 
 R4XEWM   PIC0        5    0       48     Open       3     RF73 
 R4A1FN   PIC0        5    0       48     Open       2     RF73 
 R4XSVE   PIC0        5    0       48     Open       4     RF73 
 R4VLNI   PIC0        5    0       48     Open       1     RF73


SCACP>SHOW CIRCUIT* /PORT=PEA0

This SHOW CIRCUIT command displays all circuits to all nodes.

 Circuit data for CLUIO2 at 07-DEC 12:42:23.03 
 
   Node     Port              Priority    Load    Remote_Port 
   Name     Name     State    Cur  Mgt    Class   Number  Type 
 -------- -------- --------   ---- ---- -------- ------- -------- 
 LYNX03   PEA0       Open      0    0      100      dc       NI 
 CLUIO1   PEA0       Open      0    0       10      dd       NI 
 PRMMC2   PEA0       Open      0    0       10      de       NI

SHOW IP_INTERFACE

Displays the PEdriver device IP interface data. Each device is an IP interface on the system, which can be used for NISCA communications.

Format

SHOW IP_INTERFACE ipinterface

Parameter

ipinterfacename[,...]
Includes one of more specific IP interface which you can use wildcards to specify.

Use the /EXCLUDE qualifier to exclude IP interfaces.
Use the SHOW IP_INTERFACE command to display device names.

Qualifiers

/ALL
Includes all IP interface data.
/COUNTERS
Includes device counter data maintained by PEdriver and counters.
/EXCLUDE=(IP_INTERFACES[,...])
Excludes specific IP devices, which you can use wildcards to specify.
/INTERVAL
For the /COUNTERS display, displays the changes to counters since the last SHOW command.
/n
Displays the nth page. To select a particular page of a multipage display, specify the number of the page you want to display.
/OUTPUT=filespec
Creates the specified file and directs output to it.
/SDA
Includes IP interface data displayed in the SDA format with all the data collected in one display for an IP interface.
/SUMMARY
Includes IP interface summary data. This is the default if /ALL, /COUNTERS, and /SDA qualifiers are not specified.

Example


SCACP>SHOW IP_INTERFACE/ALL

The following is a snapshot of the output for SHOW IP_INTERFACE/ALL command.
Figure 21-5 Sample SHOW IP_INTERFACE/ALL output


SCACP>SHOW IP_INTERFACE/COUNTERS

Displays IP interface counters.

Table 21-3 describes the IP/LAN device error data.

**Table 21-3 IP or LAN Device Error Data**
Data	Description
Bad SCSSYSTEM ID	Received a packet with the wrong SCSSYSTEM ID in it.
MC Msgs Directed to TR Layer	Number of multicast packets directed to the NISCA Transport layer.
Short CC Messages Received	Number of packets received were short to contain a NISCA channel control header.
Short DX Messages Received	Number of packets received were short to contain a NISCA DX header for a LAN device.
CH Allocation Failures	Number of times the system failed to allocate memory for use as a channel structure in response to a packet received by this LAN device.
VC Allocation Failures	Number of times the system failed to allocate memory for use as a VC structure in response to a packet received by this LAN or IP device.
Wrong Port	Number of packets addressed to the wrong NISCA address (Invalid cluster group number).
Port Disabled	Number of packets discarded because the LAN or IP device was disabled.
H/W Transmit Errors	Number of local hardware transmit errors.
Hello Transmit Errors	Number of transmit errors during HELLOs.
Last Transmit Error Reason	Reason for last transmit error.
Time of Last Transmit Error	Time of last transmit error:date and time.

For IP interfaces, the error count can increase for the following reasons. These errors will be displayed with any of the error codes.

The interface is unable to send data (SS$_SUSPENDED)
Link is disconnected (SS$_LINKDISCON)

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