The objective of PRACE Preparatory Access is to allow PRACE users to optimise, scale and test codes on PRACE Tier-0 systems before applying to PRACE calls for Project Access. Production runs are not allowed as part of PRACE Preparatory Access. Currently, PRACE offers the following schemes for Preparatory Access:Type A: this scheme is intended to produce scalability plots of the performance of the codes on PRACE HPC systems, as well as other parameters that may be relevant to apply for PRACE calls for Project Access. The maximum duration of Type A projects is 2 months. Type B: the objective of this scheme is to undertake code development and optimisation. Applicants will need to describe the proposed work plan in detail, including the human resources and expertise available to implement the project. The maximum duration of Type B projects is 6 months. Type C: in this scheme, PRACE experts are requested to provide the necessary support to undertake adaptations (development and optimisation) to the codes of PRACE users. The maximum support that can be requested is the equivalent to 6 person-months of effort. The maximum duration of Type C projects is 6 months. Type D: this scheme allows PRACE users to start a code adaption and optimisation process on a PRACE Tier-1 system. PRACE experts help in the system selection process. In addition to Tier-1 computing time, the PRACE user will also receive Tier-0 computing time towards the end of the project (in form of the Type A scheme) to test the scalability improvements. The work is supported by PRACE experts. The maximum support that can be requested is the equivalent to 6 person-months of effort. The maximum duration of Type D projects is 12 months.Type A (Benchmarking), Type B (Development)Access to Tier-0 resourcesHPC users and HPC communities that plan to apply to a PRACE Tier-0 call