need to increase the default dbcache size

[BrannonKing]

getnameproof fails to return the proof if there is not enough coin cache to roll back to the requested block. In the current release (12.2.3) it completely boggles the application state. In the current master it simply returns too early. We presently allow up to a 50 block rollback. Upstream bitcoin ups the dbcache to 450MB. Some rough calculations on our part show that we would need 1100MB to handle 50 full blocks. 50 full blocks is highly unlikely, but 450MB was insufficient for the use case recently demonstrated. That one required 700MB: Modify the max rollback to 5000 and run getnameproof cuphead f231bbae207d4dc5ee6cf32b5f3ae87958acdc3a40a37e32cb46c95134419f39. I propose that we up it to 700. That's not a steady state RAM usage, just an occasional spike.

[bvbfan]

It depends of block size, maximum is 2MB but most of the time is pretty lower. We can set rollback to arbitrary value say ~1000 then we can throw out of memory exception, it'll be pretty noticeable what's going on.

[bvbfan]

238

[BrannonKing]

closed via #238