How large is my Exchange Offline Address Book (OAB)?

When we perform network bandwidth planning for Exchange deployments we always ask “what is the size of your OAB?” This is important since if you have a large OAB file it can severely affect the amount of network bandwidth that you require.

One of the things that I noticed while creating and validating the Exchange Client Network Bandwidth Calculator was that many organizations did not know much about their OAB size or placement. This was tricky since I needed to know the size of the OAB so that we could predict how it might affect the network bandwidth requirements for that customer.

I decided that I would start this post to explain what the OABv4 files are, where to find them and how to determine the size of your OABv4 file J

Note: Before we dive in it is important to note here that I am concentrating on OABv4 – this was introduced with Exchange Server 2003 SP2 and Outlook 2003 SP2 (that was a long time ago!). I am hoping that everyone reading this is using OABv4 – if you’re not then it’s probably time you looked at how to upgrade since there are many benefits from OABv4 including additional stability and much better bandwidth usage.

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