Can someone explain how the message lists are built?

[Midwest Muskie]

We have users with very large (number of messages) Inbox and Sent Items
folders. I am trying to determine what is impacting the performance of these
folders. I realize that the more messages in a folder the more time it takes
to process the headers prior to displaying the list of messages. After the
list is created, are the results cached somewhere? If so, where (server or
client), and for how long? I opened a mailbox with 20,000 messages in the
Inbox, and it took 20 minutes the first time I opened it. Two days later I
opened the same mailbox and it opened quite quickly (seconds rather than
minutes). A 1,000 message folder took about 1 minute the first time, and
very quickly the next time.

Also, any thoughts on the performance difference using Cached mode versus a
direct connection to the Exchange server?

Thanks for any thoughts you may have!

Mike

 

[Roady [MVP]]

All depends on your version and patch level of Outlook.
Indexes are stored within the ost-file when CEM is enabled. Without it, it
relies on the server side indexes which could be faster (depends on your
server and connection) but adds more load on the server and requires a
round-trip every time you access the folder which makes it slower again.

 

[Midwest Muskie]

Thanks for your quick reply, Roady!

Are the indexes rebuilt or just updated when the user opens Outlook? Are
they cached on the Exchange server? Have you seen any data on number of
items in a folder and performance?

Mike

 

[Roady [MVP]]

In general the indexes are updated. Still, reading and loading the index for
the first time during an Outlook session into memory could take some time.
There is indeed a relation between the amount of items in a folder and its
loading time. Service Pack 2 for Outlook 2007 introduces some new indexes
which are much faster than before which significantly reduces loading time
of folders with loads of items in them.

 

[Midwest Muskie]

Thanks, Roady. We have not been rolling out SP2 yet, but it looks like it is
something we should be doing. It sounds like SP2 also improves the opening
of attachments as well. I've been puzzled by how long it takes to open an
attachment when using cached mode. Hopefully, SP2 will bring improvements.

Thanks again for your comments!

Mike

 

[Roady [MVP]]

You're welcome!

The slowness of opening attachments is probably caused by your virus
scanner. Many of them integrate with both Outlook and other Office
applications and often end up scanning an attachment 3 or more time because
of that before opening it (receiving, saving from Outlook, saving on hard
disk, reading when opening and reading in an Office application). Aside from
the scanning, loading those add-ins will slow down the startup of those
applications as well. Simply disable all those integration options; the
on-access scanner is sufficient.
See http://www.msoutlook.info/question/20