APING support

APING support provides the ability to test for connectivity between LU 6.2 resources, and to display pertinent routing and performance information. APING support consists of two transaction programs, APING and APINGD. The APING transaction program represents the client side of a transaction, while the APINGD transaction program represents the server side of a transaction. When a conversation is established, the client transaction program sends packets of data to the server transaction program. When the client is finished, it indicates to the server transaction program either to send the data back to the client or to send a confirmation back to the client indicating that the data has been received. The client continues the transaction until complete.

The VTAM® APING transaction program is started when a DISPLAY APING command is issued. The APINGD transaction program is started when another system in the network attempts to verify its connectivity and performance with VTAM using the APING transaction program.

Using the DISPLAY APING command, the network operator can do the following things:

Verify connectivity with any LU 6.2 resource in the network
Verify that another VTAM 4.3 or later node is operational
Check the performance of the network using a particular logon mode
Display routing information to the destination node, if a new session is established for the APING transaction

When you issue a DISPLAY APING command, the following operands determine the amount of data that is sent by the client transaction program to the server transaction program:

SIZE: Specifies the size (in bytes) of the packets to be sent.
CONSEC: Specifies the number of consecutive packets to be sent.
Note: Depending on the maximum allowed RU size on the session path, the packets might be transmitted in a number of flows different than what you specified for CONSEC.
ITER: Specifies the number of times that consecutive packets are sent to the server transaction program and returned.
ECHO: Specifies whether data is returned to the client transaction program.

For example, if you issue the command D NET,APING,ID=dluname,CONSEC=3,ECHO=YES,ITER=2,SIZE=500, as shown in Figure 1, three consecutive packets of 500 bytes are sent to the server transaction program two times, and the server transaction program returns three packets of 500 bytes two times.

Figure 1. Example of flows between client and server for DISPLAY APING command

Guideline: The maximum value for CONSEC, ITER, and SIZE is 32763. By coding 32763 for each of these operands with ECHO=YES, 32763 packets of 32763 bytes of data are sent to the partner transaction program 32763 times and the partner transaction program returns 32763 packets of 32763 bytes of data 32763 times. This could cause a significant impact to the performance of your network.

The number of concurrent APING or APINGD transaction program instances allowed can be displayed with the DISPLAY APINGTP and DISPLAY APINGDTP operator commands, and can be adjusted using the MODIFY APINGTP and MODIFY APINGDTP commands. The default instance limit for the APING and APINGD transaction programs is 10. If you need to cancel APING transaction processing, see Canceling APING sessions. The command verification exit, ISTCMMND, can be used to restrict the operands specified on the DISPLAY APING command.