LHC Optics Corrections in Run 2

The LHC optics commissioning strategy has developed significantly since the start of Run 2. The changes have mainly been driven by the decrease of $\beta$* , which was lowered from 80 cm in 2015 down to 25 cm in 2018. This has changed the impact of the nonlinear errors on the beam dynamics which, if left uncorrected, would have caused significant reduction in machine performance. As a consequence, the 2015 commissioning focused on the linear errors while the commissioning in 2017 and 2018 also included the correction of the nonlinear errors. This paper provides an overview of these changes and their impact on machine parameters and performance. It also reviews the optics stability and reproducibility. Furthermore, the focus on coupling has increased due to the understanding of its impact on instabilities and luminosity. The activity develop an automatic couplingcorrection tool was started before the run has been completed and the software is being used in operation since 2017. The drift of the transverse coupling occurs mainly at injection and a way to mitigate such a drift is proposed for the next run.