RE: Mystery "unable to extend" error

I'm not sure about that error, but if that 599124 figure is in blocks and you have 8k blocks, that's a 4.5GB extent it's trying to grab and you've only got 2.5GB free. Also, remember an extent must be contiguous so you could have lots of free space, but just not in large enough contiguous chunks. You can check the size of your free extents with the following query:  

select bytes, count(*) from dba_free_space where tablespace_name = 'USER_LOB' group by bytes;  

Regards,
Brandon  

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