User`s guide

124 DC 900-1340I
BSC Programmer’s Guide
the remote station. This is in contrast to the Send EOT command which causes the BSC
software to reject the message by sending an EOT sequence instead of ACK. In this case,
the remote station either records the data transmission as unsuccessful or attempts to
retransmit the entire message.
If the client sends a Safe Store Acknowledge command while the line is still “active”
(i.e., before an EOT sequence is received on the line), the client receives a Safe Store
Acknowledge response back from BSC signifying that the safe store operation was suc-
cessful. The TTD/WACK option (Section 6.24 on page 178) can be used to extend the
time the line is active while the client application processes the ETX block.
Note that with the safe store option enabled, the client application program must send
an acceptance (safe store acknowledge) or rejection (EOT) after every complete mes-
sage is received. Otherwise, normal data communication on the line is suspended.
If the last block of a received message contains a parity or block check error, BSC trans-
mits a NAK response as it would with any other block containing an error.
If the safe store option (Section 6.16 on page 170) is enabled while a link is active, a safe
store acknowledge response with the
dlRead pOptArgs.iICPStatus field set to 0 (success)
is generated by the BSC software and sent to the Manager session (this is the case even if
the Control session initiates the Configure Link command). The safe store acknowledge
response is the signal to the client application that safe store is now active.
An unsuccessful Safe Store Acknowledge command can return one of the following
error codes in the
dlRead pOptArgs.iICPStatus field (see Appendix D for error handling):
DLI_ICP_ERR_BAD_MODE
The function request is not available for the requested
access mode.
DLI_ICP_ERR_MODE_NOT_SAFE
The client issues a Send EOT command when BSC is
not expecting one, or an EOT is received from the