Understanding PSTs and OSTs
Definitions
If you’ve used Outlook for very long, you’ve probably come across the acronyms PST and OST. What the heck are these guys and why do you need them?
First, let’s define them in human speak:
- PST - Stands for Personal Store
- OST - Stands for Offline Store
Alright, you say, great but what are these store thingies? Well, a store is a file that Outlook uses to hold your email, contacts, calendar, tasks, notes and journal items - essentially all of your information in Outlook. So, as you can readily see, the stores are very important files.
Which File Type To Use?
Unless you are using Outlook on a corporate network, Outlook stores your information in a PST file. OST files are only used in corporate networks where Outlook is running in cached mode and connected to a Microsoft Exchange server. However, this doesn’t mean you aren’t using PSTs as well. So, let’s verify by checking out the Outlook data file types you are using.
In Outlook 2007:
- Go to File –> Data File Management
- Select the Data Files tab
As you can see above, I’m using two PST files - archive.pst and Outlook.pst. The file location on your local computer is displayed to the right of the file name, so if you ever need to know its location you can find the information from the Data Files tab.
In Outlook 2003:
- Click File –> Data File Management
Other Notable PST and OST Info
- Outlook 2002 and earlier are limited to PSTs no larger than 2GB in size. Outlook 2002 and earlier PST files are in ANSI formate
- Outlook 2003 and later use UNICODE format and can use much large PST files - up to 20 GB by default. Microsoft has an article discussing how to change the size of PST and OST files.
