Lookout PST files

As you know, I am not Microsoft’s biggest fan and I am always encouraging people to look at alternatives. Our local secondary school could save a fortune each year if it didn’t pay for Microsoft licences and used Linux instead of Windows and OpenOffice instead MS Office. While I think the Microsoft products are satisfactory in their way, I’m just amazed at how many people can’t picture a world outside of Microsoft products. I ask whether they have tried Web-based applications, but too many are Microsoft zombies, or else argue that they need to use the products at work and so find it convenient to use them at home.

And this, in a roundabout sort of way, is how I’ve ended up discussing Microsoft Outlook PST files in this week’s blog.

Microsoft Outlook stores messages, contacts, appointments, tasks, notes, and journal entry data in Messaging Application Programming Interface (MAPI) folders. These MAPI folders can be stored in either a mailbox located on Microsoft Exchange Server (if you have it), or a personal folder (.pst file) on a local hard disk. PST stands for Personal Storage Table.

With Outlook 97 the PST file was encoded in ANSI format and had a maximum file size of 2GB. With Outlook 2003 and 2007 the PST file is encoded in unicode format and has a maximum size of 33TB. PST data can be imported or exported using the File/Import and Export… menu item.

Microsoft recommends that personal folders should be used only by Outlook users who access Internet mail only (ie do not use an Exchange Server). Microsoft also recommends that apart from mobile users who need to access data while offline, Exchange users should store all messages within the Exchange information store rather than in a personal folder.

A big problem users have with PST files is recovering from some kind of file corruption. One way to recover is to use a back-up copy of the file. However, if PST files are stored locally, there is a strong chance that they won’t be backed up. If they are stored on a network server, they won’t be backed up if they are open – ie if a user stays logged on overnight. Another problem with using a network server is performance. If lots of users update their PST files, the amount of messages sent and received can place a huge load on the network.

Another way to recover PST data is to use the Inbox Repair Tool (SCANPST.EXE), but this cannot always recover all the data. The Inbox Repair Tool rewrites the PST file’s header information, and deletes anything in the file it can’t understand. This means it’s good at repairing damaged header files, but less good at recovering damaged data.

There is also a performance issue with PST files and Outlook 2007. The Microsoft Knowledge Base article 932086 says that users may experience performance problems when working with items in a large PST file or in a large OST file. It goes on to suggest that part of the reason for the slowdown is a new internal structure for PST and OST files that increases the amount of disk access. The patch optimizes the way writes are committed to OST and PST files. Microsoft originally recommended that users kept the default PST file as small as possible, eg using AutoArchive to move out messages older than a few months.

An OST file, by the way, is an Outlook offline folder file. Users can work offline and then synchronize any changes with the Exchange server when they next connect.

So there we are, in this my 101st blog, I have turned to the dark side and talked about something to do with a Microsoft product. What next, Silverlight and XAML??