Asynchronous Terminals and Printer Processes Programming Manual

PRINTER PROGRAMMING CONSIDERATIONS
DELAYTIME SYSGEN Modifier
The 100 multiplier converts the time into 10-millisecond units;
the 2 multiplier provides a safety factor.
If you don't know the low-water mark, use the following formula
to determine a safe value for DELAYTIME:
DELAYTIME = [[buffer size / speed] * 100 * 2]
XFERSIZE SYSGEN Modifier
The XFERSIZE n modifier specifies the maximum number of bytes
transmitted per transfer. If a data line exceeds XFERSIZE, the
I/O process breaks the line up into bursts of XFERSIZE. XFERSIZE
applies only to DTR with RC. The default XFERSIZE is 40.
The following formula shows how to calculate the recommended
value for XFERSIZE based on the printer's buffer size and high-
water mark:
XFERSIZE = [buffer size - high water mark]
The buffer size and high-water mark (both expressed in number
of characters) should be available from the printer vendor's
specifications.
Spooler Restart and Recovery
When using DTR, RC, TPAUSE, or REVTPAUSE flow control, the
printer provides busy/not busy status, but no detailed status
information.
The I/O process returns the file-system error 100 to the spooler
for all printer I/O timeouts. Error 100 allows operator-
correctable faults to be retried. However, if the printer
fault is not recovered before the retry period expires, the
spooler places the printer in the offline state. In the spooler
operating environment, a printer offline indication provides
general information only; it does not suggest any reason for the
condition.
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