Address Lists reside in AD while OAL is put under Exchange system public folder
You can create as many as AL as you wish. The most used AL is GAL, created by Exchange setup by default.
An OAB can contain many OAL's,
An OAL can specify more than one AL's, but a user can download only one of them
A mailbox store is associated with an OAL
Default AL is associated with any newly created mailbox store
Before OAL's can be generated, the address lists, on which OAL based, in Active Directory must be up-to-date. The Exchange SA service calls RUS to maintain AL's. If RUS cannot populate the AL's, Exchange cannot build the OAB's.
once you create a new OAL, you have to wait for public folder store online maintainence to happen overnight to populate messages/attachments into OAB folders
When you delete an OAL, the server dosen't remove the corresponding system folder for 7 days, so if you create a new offline address book with the same name, it is added as OAB version 2 in a subfolder. When this happens, the outlook client can't find the OAB since it is in a folder instead of in System Folder directly.
An OAB server is the server that generates those messages/attachments, it has to be one of the replica server (Q286328)
Default OAL contains data from GAL, but you can populate it with any other ALs. Even you can put more than one ALs into one OAL, but only one AL will be used.
It's often desired to associate different OAL to different mailboxes