public override void Init(int flowCount, long flowRecordCount)
{
mapId = new UInt64();
session = new SessionNoServerShared(DataDirectory);
session.BeginUpdate();
session.DefaultDatabaseLocation().CompressPages = false;
session.RegisterClass(typeof(VelocityTick));
session.RegisterClass(typeof(BTreeMapOidShort <long, VelocityTick>));
}