User`s guide

176 DC 900-1340I
BSC Programmer’s Guide
ing messages could deplete the buffer supply and the other links would not be able to
obtain buffers.
To prevent this from occurring, a queue limit can be placed on the BSC-to-client mes-
sage queue for a particular link. When the queue limit is reached, the last buffer on the
queue is marked with the
DLI_ICP_ERR_QFULL error code, and all subsequent blocks from
the link are discarded until the client program begins reading messages from the queue.
BSC sends NAK for all data blocks that cannot be put on the queue. Control blocks such
as data acknowledge, status report, etc. that cannot be placed on the queue, are dis-
carded. When the client program receives the
DLI_ICP_ERR_QFULL error, it should check
the sequence number to determine how much data, if any, was lost.
The client program specifies the maximum number of buffers to be placed in the BSC-
to-client queue for a particular link. The queue limit applies to all sessions for a given
link. For example, if a queue limit of ten is set on a link that has Manager, Read, Control,
and Trace sessions established, the BSC software queues ten master buffers, ten read
buffers, ten control buffers, and ten trace buffers. The queue limit is also independent
for each type of session; for example, if the Manager session has all ten buffers queued
and waiting to be read, this does not affect the Control, Read, or Trace session’s ten-
buffer limit.
Specify a zero value to disable queue limiting for a link.
To set this option using the DLI configuration file, use the qLimit parameter; for exam-
ple,
qLimit = 0. See Table 7–2 on page 191.
6.20 EOM Line Control Option (22)
The BSC 2780/3780 EOM line control option controls the line reverse that occurs after
the software sends an EOM block. There are four options: reverse, hold, permanent hold,
or permanent hold with notify.