General
Information
Mirror
Image Backup. A mirror image backup is basically a
cylinder-for-cylinder copy from the source to the destination disk.
(Only those cylinders that actually contain data are copied.) When the
backup
is
complete, the destination disk
is
an
exact copy, or mirror
image, of the source disk.
Backup
By
Class. A backup
by
class takes place if you specify a
partspec or any parameter except X or MPW
in
the command line.
Backup
Reconstruct. A backup
by
class
and
a backup reconstruct
function identically. The only difference
is
that while
you
initiate a
backup
by
class, the system initiates a backup reconstruct.
On
certain TRSDOS application programs, you can only make a
limited number of backups.
And,
when you make a backup
on
one of
these programs, the source disk has
to
be
write-enabled during the
backup or the backup fails.
Backups
With the (X) Parameter. This parameter allows you
to
back
up
data disks of different sizes or capacities
on
a two-drive system
(using backup reconstruct). One-drive system can perform
mirror-image backups only. When you use the
(X)
parameter to
backup non-system disks of different sizes or capacities, system
modules
2,
3 and
10
must first
be
put into memory with the SYSTEM
(SYSRES
=number) command. Remember that the (X) parameter
is
used only when there
is
a non-system disk
in
Drive
0.
Mirror
Image Backup. TRSDOS makes a mirror image backup if the
source and destination disks' size
and
density are identical, and if you
specify
no
partspec
or
parameters (except X or MPW)
in
the
command line. The number of cylinders doesn't need to be identical
as
long
as
the destination disk has at least
as
many cylinders
as
the
source disk.
The date
on
the destination disk shown with the DIR or FREE library
commands is changed
to
the current system date.
After the backup, the destination disk has its directory
on
the same
track as the source disk regardless of where it was before the
backup. The information
on
the destination disk
is
updated to reflect
its true cylinder count
and
available free space.
Backup
By
Class. This type of backup does a file-for-file copy from
the source
to
the destination disk. Files that are fragmented (spread
over more than one extent)
on
the source disk are consolidated (if
possible)
on
the destination disk.
Unlike a mirror image backup, files that exist
on
the destination disk
but are not
on
the source disk are not touched
in
the backup. When
the backup
is
complete, the destination disk contains
all
files moved
from the source disk plus any other files that existed
on
the
..
~"
destination disk before the backup began.
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