Increasing the Expressiveness of Analytical Performance Models for Replicated Databases

. The vast number of design options in replicated databases requires efficient analytical performance evaluations so that the considerable overhead of simulations or measurements can be focused on a few promising options. A review of existing analytical models in terms of their modeling assumptions, replication schemata considered, and network properties captured, shows that data replication and intersite communication as well as workload patterns should be modeled more accurately. Based on this analysis, we define a new modeling approach named 2RC (2-dimensional replication model with integrated communication). We derive a complete analytical queueing model for 2RC and demonstrate that it is of higher expressiveness than existing models. 2RC also yields a novel bottleneck analysis and permits to evaluate the trade-off between throughput and availability. 1 Introduction Replication management in distributed databases concerns the decision when and where to allocate physica..

Determination of |V(ub)| / |V(cb)| with DELPHI at LEP

The ratio of the CKM quark-mixing matrix elements |Vub|/|Vcb| has been measured using B hadron semileptonic decays. The analysis uses the reconstructed mass M_X of the secondary hadronic system produced in association with an identified lepton. Since B -> X_u lepton anti-nu transitions are characterised by hadronic masses below those of the D mesons produced in B -> X_c lepton anti-nu transitions, events with a reconstructed value of M_X significantly below the D mass are selected. Further signal enrichments are obtained using the topology of reconstructed decays and hadron identification. A fit to the numbers of decays in the b -> u enriched and depleted samples with M_X above and below 1.6 GeV/c^2 and to the shapes of the lepton energy distribution in the B rest frame gives |Vub|/|Vcb|= 0.103^{+0.011}_{-0.012} (stat.) +/- 0.016 (syst.) +/- 0.010 (model) and, correspondingly, a charmless semileptonic B decay branching fraction of BR(B -> X_u lepton anti-nu) = (1.57 +/- 0.35 (stat.) +/- 0.48 (syst.) +/- 0.27 (model)) x 10^{-3}.Comment: 24 pages, 8 figure