MPE/iX Commands Reference Manual (32650-90877)
558 Chapter13
Command List XI
Commands SHOWLOG thru STORE
serial printer does not return page data to its storage manager.
The storage manager does not attempt to interpret the spool file data,
looking for escape sequences that may advance paper, eject a page, or
change the page length or line density. This would degrade performance to
an unacceptable level. Instead, it checks the carriage control character
supplied as part of the user's FWRITE intrinisc call.
If that character is an ASCII "1" or an octal 300 (indicating skip to VFC
channel 1, which by industry standard, is a page eject), it notes that this
type of page control is in use and assembles its own checkpoint based on
the location of this record in the spool file. If a RESUME with OFFSET is later
required, it counts these checkpoints to try to find the proper restarting
point. The storage manager ignores any other carriage-control character.
The page eject carriage control is not required in user data, and many
applications do not use it. In this case, the storage manager is forced to
assume a static number of records (60) per page. Historically, this is the
number of lines that fit on a standard 11-inch page at 6 lines per inch,
allowing three lines of margin at the top and the bottom of the page. This
is often a flawed assumption, as the following examples show:
• For many applications (for example, A4 paper, 8 lines per inch, and so
on) 60 lines per page is the wrong value.
• Other applications are designed for specific forms and manage their
own paper advancement. These applications may attach a
carriage-control value to a record which causes paper to advance (say)
five lines after printing a line of data. The storage manager counts this
as one record.
• Control records (those that affect some aspect of printer operation but
do not print anything) are included in the 60 record count.
The last two examples come about because the storage manager does not
interpret the data in the spool file, as mentioned earlier, and so cannot
detect these situations.
In summary, if the storage manager cannot interact with the device to
determine page boundaries, it uses a carriage control "1" or %300, or 60
records per page to simulate checkpoints for SPOOLER
ldev
;RESUME.
Therefore, for the most consistent results with serial printers you should
always include an OFFSET=1 parameter, with the SUSPEND option. You can
also include the parameter with a subsequent RESUME option, but this does
not prevent another spooler process from printing the file from the "wrong"
place in the meantime.
SHOW The SHOW parameter displays the status of the spooling process(es)
associated with the device(s) specified. All other parameters on this
command are processed first, so the SHOW option reflects the updated state
of the process(es) at the completion of the command executor. Please refer
to the note following the example below.
OPENQ The OPENQ option or parameter enables spooling for a specified logical