https://bugs.openldap.org/show_bug.cgi?id=10275
--- Comment #1 from Howard Chu hyc@openldap.org --- Increasing the batch size is a bit risky, since it doesn't take into account transactions with very large data items, which could overflow the txn dirty list and cause page spills - which would then reduce performance, defeating the point of this.
It probably would be better to add a NoSync option instead, if all you want is the fastest possible load time.