  The prototype of the Large-Sized Telescope (LST) of the Cherenkov Telescope
Array (CTA) is presently going through its commissioning phase. A total of four
LSTs, among others, will operate together at Observatorio del Roque de Los
Muchachos, which will host the CTA North site.
  A computing center endowed with 1760 cores and several petabytes disk space
is installed onsite. It is used to acquire, process, and analyze the data
produced, at a rate of 3~TB/hour during operation. The LST On-site Analysis
LSTOSA is a set of scripts written in Python which connects the different steps
of lstchain, the analysis pipeline developed for the LST. It processes the data
in a semiautomatic way producing high-level data and quality plots including
detailed provenance logs. Data are analyzed before the next observation night
to help in the commissioning procedure and debugging.
