ACC Utilities Reference Guide

TTGEN - ZCOM System Table Generator
Creating the TTGEN Configuration File
Chapter 2 63
When the number of pending messages on the ZNODE queue reaches the
high-water mark, programs initiating remote requests are suspended to
avoid excessive buffers being held on the ZNODE queue. When the
number of messages in the ZNODE queue drops below the low-water
mark, such suspended programs are allowed to resume execution.
Note that this mechanism is only applicable to programs initiating
remote requests and does not limit the messages or responses generated
as a result of ZCOM subsystem operation (e.g. when a terminal returns a
message to its receiver on a remote system).
There is one special provision provided to prevent the ZCOM subsystem
from suspending programs issuing remote requests. If the low and high
water marks are set to the same value, issuing a remote request when
the number of messages on the ZNODE queue is at or above the
high-water mark will cause the request to be rejected immediately with
the error code ZENBUSY (-1).
If the Flow-Control parameter is not specified, then a default low-water
mark of 0 and high-water mark of MAX_INT is used (e.g. flow control is
disabled).
Local-Node
The node definition for the local system. If Node-Definition is specified,
then Local-Node is mandatory, regardless of whether any remote nodes
are defined. The parameter is the node number of the local node. Only
one local node can be defined.
Remote Node
The node definition for remote nodes. Multiple “Remote-Node”
definitions are allowed. Each entry defines the configuration of one
remote ZCOM system. The <node> field is a unique number identifying
the remote system. The <timeout> field specifies the maximum time (in
seconds) to wait for a response for a request sent to this remote system.
The <hostname> field is the alias name or IP address (in dot format) of
the remote system. Up to 4 hosts names may be specified (one for each
LAN card), and the traffic load is shared between the hosts. The specified
host names must be defined in the “/etc/hosts” file.