What is O2?

The Online-Offline (O2) software serves as a general purpose software framework for the full computing pipeline of ALICE. A more detailed breakdown can be found in the technical design report at: O2 TDR.

The software can be divided into the following parts:

• O2 Core
• O2 Physics (Documentation: O2 Physics Docs)
• O2 DPG (simulations) (Documentation: O2 Sim Docs)
• Quality Control

All of the parts strictly require O2 Core to be installed as the base. It is also highly recommended to install O2 Physics, as it is needed in most cases to access and analyse data. The other parts can be selectively installed based on specific usage requirements.

In addition to the mentioned parts, there is also the Grid and CCDB. The Grid is where all of the experimental and simulation data of the experiment is stored, and where computing jobs are managed - it can be accessed in the browser via the MonALISA interface. The CCDB is a database and rest API that stores important information and configurations of the ALICE detector during data-taking. As an O2 user, you will not have to access the CCDB directly - only potentially in the case when doing O2 development.