Consultor Eletrônico

CD-ROM Installation Fails

DRAFT COPY - Currently under review and edit.

INTRODUCTION:
=============
There are often times when doing installs where errors will pop up
indicating that an Application Error has occured or that there is
insufficient memory or that a file can not be found. The purpose
of this KBase is to define some common reasons why this can occur
as well as provide some ways to test and or resolve the problem.

WHY YOU NEED TO KNOW THIS:
===========================
By attempting some of the suggestions contained within this document
you may be able to help identify whether the problem is with the media
or with the hardware you are using.

PROCEDURAL APPROACH:
====================
Some things that can be checked for these types of errors are:
1) Is the cd clean and free of scratches and smudges?
2) Is the cd in the drive?
3) Is the cd shiny (non-label) side down in the tray or caddy?

If the cd is clean and scratch/smudge free and is in the tray or caddy
correctly and you are getting errors then the next thing to do is.....

1) If this is a Windows 95 or NT machine go into your "My Computer"
icon and make sure you have a cdrom icon.
If you don't have an Icon, then you need to make sure your machine
either has a cdrom drive internal to it or whether you have made
a connection to a cdrom which is on another machine but is shareable
through the network.
2) Try installing the product on another machine which has a
different cdrom drive.
Perhaps the cdrom drive is damaged? Or, in some cases a
manufacturer may have made their cdrom drive with limitations on the
amount of info that can be read from cdrom.

GENERAL INFO ABOUT CD's
=======================
When a cdrom is made, it is written in 1 of 2 modes.
Mode 1 cdroms have to be read in Mode 1 and Mode 2 cdroms have
to be read in Mode 2.
Mode 1 cdroms were written with CRC (Cyclical Redundancy Check)
information to guarantee that the information written on the
cd is what is being received by the application.
The way it usually can tell is, just before the read of information,
a certain value is passed to the application which tells it the
data value it should arrive at when it has read the info from cd
and perform a quick formula calculation.
If the CRC value doesn't match what is read, the application will
usually try and re-read the data again and again for a certain number
of times before it will report that it was unable to read the info or
it will succeed and go to the next bit of data.
Sometimes if the cdrom is dirty, the value it gets from the CRC
will not match the value of the data and so it errors out.
A scratch or a smudge or even excess dust can cause this problem.
In fact, anything which could theoretically block or bend the light
and interfere with the read of the data will have this type of effect.
Normally the application is designed to retry the attempted read of
information a number of times before it is programmed to give an error
message.

In some cases, if the cdrom drive has been manufactured only to be
able to read so much data from the cd (not because it knows
anything about the data but because its internal mechanism can only
move a certain distance), this can cause variations on the errors that
will be generated. The common type of errors that will occur are
random problems reading either the same or constantly changing file
names. This can lead to GPF's (General Protection Fault) or
Application errors when the install program tells the cd to read
info from a file. The cdrom drive tries to go to the spot on the cd
where it was told to grab the file. It starts reading the file but
never gets to the end of the file because the end of the file is
beyond the limit it can read data. Since it hasn't reached any marker
saying it can stop reading, it just keeps reading data...
filling up memory...
reading data...
filling up memory.
Eventually it runs out of memory or resources and causes an error.

RAS 11/25/97

Progress Software Technical Support Note # 17433