For most applications, the WLM server-specific recommendations
provide a more accurate way to distribute workload to the servers.
However, when a server acts as an access point to applications that
run in other address spaces (and therefore in a different service
class), WLM system weights might be the preferred distribution method.
For example:
- The TN3270E Telnet server (Telnet) is a communication gateway
function that enables clients to access SNA applications over an IP
network. As a result, most of the actual work associated with a Telnet
workload takes place in the SNA application, which is typically classified
to a different WLM service class than Telnet and probably at a lower
importance level. Therefore, although the WLM server-specific recommendation
can provide an accurate assessment of how well an individual TN3270E
Telnet server is performing, it does not necessarily provide an accurate
assessment of the available capacity required by the back-end SNA
applications that the client is accessing. As a result, WLM system
weight is probably a more appropriate distribution method for this
server.
- The INET daemon also provides access to other applications that
are probably associated with service classes of a lower importance
level (for example, z/OS® UNIX Telnet, REXECD, and RSHD).
As a result, similar considerations apply, and WLM system weights
are the more appropriate distribution method for this server.
- The FTP daemon address space typically performs very little processing
on behalf of new FTP sessions. After accepting a new connection, it
performs a fork() for an FTP server process that will service the
new FTP session. The FTP server process is classified again by WLM,
possibly resulting in a different service class than that of the FTP
daemon.
- If the FTP servers run in a different service class than the FTP
daemon, then WLM system weights should be used.
- If WLM policies are set up so that the FTP servers are classified
in the same service class as the FTP daemon, WLM server-specific weights
should be the distribution method. Although the WLM recommendation
will not take into account how well the actual FTP server is meeting
its goal, the recommendation will more accurately reflect the amount
of displaceable capacity because it is based on the importance of
the service class.