Commit and sessions

[Per Steffensen]

Hi

If I have added some document to solr, but not done explicit commit yet, 
and I get a power outage, will I then loose data? Or asked in another 
way, does data go into persistent store before commit? How to avoid 
possibility of loosing data?

Does solr have some kind of session concept, so that different threads 
can add documents to the same solr, and when one of them says "commit" 
it is only the documents added by this thread that gets committed? Or is 
it always "all documents added by any thread since last commit" that 
gets committed?

Regards, Per Steffensen