  The CMS offline software and computing system has successfully met the
challenge of LHC Run 2. In this presentation, we will discuss how the entire
system was improved in anticipation of increased trigger output rate, increased
rate of pileup interactions and the evolution of computing technology. The
primary goals behind these changes was to increase the flexibility of computing
facilities where ever possible, as to increase our operational efficiency, and
to decrease the computing resources needed to accomplish the primary offline
computing workflows. These changes have resulted in a new approach to
distributed computing in CMS for Run 2 and for the future as the LHC luminosity
should continue to increase. We will discuss changes and plans to our data
federation, which was one of the key changes towards a more flexible computing
model for Run 2. Our software framework and algorithms also underwent
significant changes. We will summarize the our experience with a new
multi-threaded framework as deployed on our prompt reconstruction farm for 2015
and across the CMS WLCG Tier-1 facilities. We will discuss our experience with
a analysis data format which is ten times smaller than our primary Run 1
format. This "miniAOD" format has proven to be easier to analyze while be
extremely flexible for analysts. Finally, we describe improvements to our
workflow management system that have resulted in increased automation and
reliability for all facets of CMS production and user analysis operations.
