a billion? Wow! First, I really, really, really doubt you can use a RAMdir to index a billion documents. I'd be interested in the parameters of your problem if you could. I'd be especially interested in providing a home for any of your old hardware, since I bet it beats mine all to hell <G>.
Second, you'll just have to play with the MergeFactor and MaxBufferedDocs to see how high you can set them on your particular machine (using an FSDir). Then reduce those factors by a pretty major amount (I'd recommend maybe 1/4 the size that runs out memory on your test data set). The last thing you want to do is cruise through 900,000,000 documents and find the particular set of data that causes an exception... Actually, I'd guess you're better off indexing the documents in smaller groups and combining the indexes afterwards. That way, you place an upper limit on how much work is lost if you have any problems, as well as parallelize the index creation process. Assuming you have the hardware. Best Erick
