user may alter the characteristics only of those files that have an
owner's userid that matches his own, whereas the system operator may change any spool file in the system.
Each spool file in the system has a number of attributes that are
assigned to it, either explicitly or by default, at the time that it is
created. These attributes and their values are as follows: • Filename and filetype can be 24-character fields. Either or both
can be replaced by a user-supplied val ue. • Spoolid number is a system-assigned number between 1 and 9900. It
is automatically assigned when the file is created (input) or closed
(output), and is unique within the system. The file;s owner, the device type, and the id number are specified. Usually, the userid
defaults to the identification of the user issuing the given
command. Because the identification number rather than the filename and filetype is an identifier, duplicate user-assigned names do not
present an identification problem. • The number of logical records (cards or print lines) in the file is
an integer between 1 and 16 million5 For printer files, the record
count also includes any immediate operation code space or skip CCWs. • The originating user is the identification of the file's creator, if
the file has been internally transferred from the originator's
printer or punch to the new owner's card reader. • The number of copies requested for an output file is between 1 and
99. Unless altered by the user or operator, it defaults to 1. • The device type is used by DIAGNOSE for a file transferred to a
reader to determine the virtual type of output device. I. CHARS for 3800 printer I. FCB for 3800 printer I. MODIFY for 3800 printer I. FLASH for 3800 printer
In addition to those attributes, a file that is queued for real
output or virtual input always has a class associated with it. 1 class
is a single alphameric character from 1 through z or from 0 to 9. It
controls both the real or virtual device on which the file will be
printed, punched, or read, and the relative priority and sequence of
output on the device. While each file is assigned a single class, each
real spooling output device can be assigned from one to four classes.
The device then processes only files that have a class attribute that
corresponds to one of its own, and processes these files in the order
that its own classes are specified.
For example, if a printer is assigned the classes A, D, 2, it
processes any printer file with a class of A before it searches the
printer output queue for a file with class D. All class D files are
printed before class 2 files.
The output class for a file is assigned at the time the file is
created and is the class that is associated with the virtual device that
created it. While each real spooling device can have up to four
CP Introduction 1-145

classes, each virtual spooling device can have only one. When a user
logs onto to the system, the class associated with a device is the one
defined in his directory entry for that device. However., he can alter
this class at any tiae by the SPOOL command. As files are created and
closed by a device, they take on the device's output class.
After they are closed and are awaiting output, their class can be
changed by a CHANGE command issued either by the file's owner or the system operator. The system operator can alter the systea generated
output class(es) of a real output device by the START co.aand. Output files transferred to a user's virtual reader can also be
controlled by class. If the receiving user has several readers, the
input to each can be liaited to files of a certain class. In addition,
the ORDER command allows sequencing of input files by class as well as
spoolid number. Output priorities can also be managed by altering the hold status of
a file. Individual users can alter the hold status with the CHARGE command, while the system operator can change (hold or free) the files
of specific individual users. SPOOL and CHANGE coamands can be used to modify the CHARS, FCB, MODIFY, and FLASH attributes of a file or a virtual printer.
These commands affect the status of a user's virtual spooling devices: SPOOL Meaning Terminates spooling operations on a specified device. It
clears the device of any pending interrupt conditions, and for
output files, updates the tag record, completes and queues the
file for real output. Optional operands allow the user to
specify a filenaae and filetype, and to override for the given
file any standard CLASS, HOLD/NOHOLD or COpy operands set into
the output device by the SPOOL command. Establishes the file attributes that apply to files created
on, or read by, the given device. It establishes the class
that will be in effect, whether: files are to be autoaatically
held, input files are to be saved or purged after reading, and
output files are to be directed to the real systea printers
and punches or are to be transferred to a user's virtual
reader. The SPOOL command also specifies 3800 attributes.
The operator can use these commands to control the activity of the real
spooling devices: Backspaces an active spooling device for either a specified nuaher of pages (printers only) or to the beginning of the
file (printers or punches).
DRAIN Stops the operation of a specified output or input device
after it has finished processing the file on which it is
currently working. A printer must be drained prior to the
issuance of the LOADBUF command. Unit record devices are
normally drained prior to system shutdown.
1-146 IBM VM/370 System Logic and Problem Deteraination--Voluae 1