I am setting up a tablespace to store BLOBs. I want to use a locally managed tablespace with uniform extent. How are the LOB segments allocated within the tablespace? What is an appropriate uniform extent size for the BLOBs?
LOB segments are no different than any other segments when it comes to allocating space. LOB segments will use whatever allocation method is defined for that tablespace.
At this point, I would like to suggest that you use the AUTOALLOCATE method for your Locally Managed Tablespace. I use LMTs with AUTOALLOCATE exclusively for my tablespaces. I stopped thinking about extent sizes over two years ago and have never looked back. Why worry about an "appropriate uniform extent size" when Oracle and AUTOALLOCATE does a really good job of worrying about extent sizes for you? Change your LMTs to AUTOALLOCATE and start living!