KB 1000125 is useful. However take a local backup of DB from SQL and purge the stats.
There are known issues reported in vCenter U1 where stats rollup job (specifically the daily job) will continuously run and increase the transaction log history. Note, this issue occurs only with vCenter U1 under specific environments.
Thanks,,
Ramesh. Geddam,
VCP 3&4, MCTS(Hyper-V).
Please award points, if helpful