Example 1

An application provides 3270 emulation over Telnet. It needs to connect to any LU available in its configured LU Pool of ACCOUNTS, and it needs to connect through the lightest loaded server. No scopes are configured in the network. The mainframe host supports dynamic device types so the application does not need to specify a device type.

The application begins by issuing the following predicate for the SL_GetService request to locate a server (in all examples '\t' is the TAB character):

tn3270//LUPOOL==ACCOUNTS*/

At this point, a list of three URLs (similar to these) is returned (the port number 23 is the standard port for Telnet connection requests):

service:tn3270://9.37.51.254:23
service:tn3270://9.37.51.260:23

service:tn3270://9.37.51.256:23 

Being designed to perform least-load location, the application issues a series of SL_GetAttrs calls directed to each URL to obtain the load measurement of each server. It specifies a select clause similar to the one below to receive only load information:

URL = service:tn3270://9.37.51.254:23
Attribute filter = LOAD

• The attribute LOAD is returned along with its value "5"
• The application issues a second SL_GetAttrs for the second URL and its load is returned, "2"
• And finally the third server, which returns a load of "10"

Since the load for the second server is lower, the application selects 9.37.52.260:23 as its connection target. The application tries to connect through 9.37.51.260, but the connection fails since no LUs are available. It then tries to connect through 9.37.51.254 (the next least-loaded server) and this time, it succeeds.