Owner`s manual
Page 6-6 Chapter 6
the same controller. Also, several types of hard drives can run under the control of the
same Hard Disk Controller—but because these devices are different sizes, each type
may have to have its own name and bitmap area. See your
System Operator’s Guide
for information on hard disks.
The BITMAP command specifies the name of the device the bitmap is for. AMOS then
sets up the bitmap for that device. There are three ways the BITMAP statement can
appear, depending on what type of disk you have, and whether or not you are using
paged bitmaps. Use the appropriate type of bitmap statement for your computer.
Non-self-configuring drives on computers without paged bitmaps require the three-letter
name of the drive, the bitmap size, and the numbers of the logical units for that drive.
For example:
BITMAP DSK,4311,0,1,2,3
On self-configuring drives AMOS can automatically read the bitmap size from the disk. If
your disk has this capacity, you may leave out the bitmap size (but leave the comma)
when you specify the line. For example:
BITMAP DSK,,0,1,2
If your computer supports "paged bitmaps," and you are using a SCSI disk, you only
need to specify the three-character device name. A paged bitmap is one only partially in
memory, thereby saving memory space. The portions of the bitmap needed at any given
time are "paged" into memory from the disk. For example:
BITMAP DSK
Paged bitmaps are especially useful for large disks, but may be inefficient if used with
small devices such as floppy disks. You may want to use paged bitmaps for your large
drives, and traditional format bitmaps for smaller devices.
For information on the number of words needed for the bitmap of a particular floppy disk
device, and information about hard disks, see your
System Operator’s Guide
.
The monitor builds one sharable bitmap area in memory for each BITMAP command it
finds. The BITMAP command also specifies the disks to be accessed by SYSTAT when
SYSTAT prints the number of free blocks left on the devices.
6.6INCREASING THE SYSTEM QUEUE SIZE
The monitor has a general purpose queue system that several AMOS commands use,
and which is also available to user programs. The queue contains a fixed number of
longword blocks which are assigned and then returned during the course of processing.
The number of queue blocks you need depends upon the size of your monitor and the
tasks it performs.
System Operator’s Guide to the System Initialization Command File, Rev. 03