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Q148515: XCLN: How the Exchange Windows 95 Client Uses Control.glb

Article: Q148515
Product(s): Microsoft Exchange
Version(s): WINDOWS:3.2,3.2a,3.5,4.0
Operating System(s): 
Keyword(s): kbusage
Last Modified: 24-MAR-1999

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The information in this article applies to:

- Microsoft Exchange Windows 95/98 client, version 4.0 
- Microsoft Mail for PC Networks, versions 3.2, 3.2a, 3.5 
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SUMMARY
=======

When you use the Microsoft Exchange client for Windows 95 to communicate with a
Microsoft Mail 3.x postoffice, Control.glb is not incremented after every
message sent.

MORE INFORMATION
================

Control.glb is an eight byte file. The first four bytes are used to store a hex
number that is used to create the unique file prefix used to name all the
database files that are unique to the new user. The second four bytes are used
to store a hex number that is used to generate names for new messages and
attachments as the are created and written to the Postoffice.

The Microsoft Exchange client for Windows 95 performs a caching function that
opens Control.glb, retrieves five hex-id's, and then increments Control.glb
accordinly. The client then caches the extra hex-ids anticipating that the user
will send more mail during the session. This process reduces the number of times
that the Microsoft Exchange client for Windows 95 must access Control.glb, thus
reducing the possibility of file contention problems. This process does not
expose the mail database to corruption, however, this will affect utilities such
as Traffic.exe that use the Control.glb counter as a method of tracking the
number of messages and attachments processed by that postoffice.

The Microsoft Exchange client for Windows 95 also automatically creates an
attachment for every mail message sent in Rich Text Format (RTF). This is a
hidden attachment named Winmail.dat that contains the information needed to
display RTF on another Microsoft Exchange client. Because of this, the Microsoft
Exchange client for Windows 95 will use at least two Control.glb numbers for
each mail message sent; one for the message and one for Winmail.dat. Each
additional attachment uses another distinct Control.glb number.

When a message with an attachment is sent, the attachment is created and stored
in the appropriate ATT subdirectory. File names for attachments, or ATT's, are
made up of an 8-digit hex number created from the right 4 bytes of Control.glb
and followed by an AT(#) suffix. For example, 00001b45.att is an attachment and
is stored in the \ATT\AT5 directory. Federal Information Processing Standard
(FIPS) format dictates that the attachments are owned by the messages. Since the
attachment, .ATT, was created first, the hex-id of the ATT is stored as a field
in the message. If there are many attachments, each hex-id uniquely generated by
Control.glb is stored in the message. The mail message itself follows the same
naming and storage conventions as attachments.

Additional query words:

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Keywords          : kbusage 
Technology        : kbExchangeSearch kbExchangeClientSearch kbZNotKeyword kbZNotKeyword2 kbMailSearch kbZNotKeyword3 kbMailPCN320 kbMailPCN320a kbMailPCN350 kbExchange400Win95
Version           : WINDOWS:3.2,3.2a,3.5,4.0

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