A Data Entry is a collection of potentially all IDS
Multiple occurrences of a given IDS can co-exist, e.g. multiple equilibria calculated by different codes / assumptions
A Data Entry is defined by:
- IMAS version
- User name
- Machine name
- Pulse number
- Run number
The recommended usage for a Simulation is that
- The simulation starts by reading data from an Input Data Entry (can be the from of another User)
- During the simulation, intermediate results are stored in a temporary “work”
- Entry (another Run number)
- During or at the end of the run, the results intended to be archived are written to an Output Data Entry (Run number)

Where to find your local IMAS data repository ?

Answer #1: you do not care because the Access Layer will know where to find it
Answer #2: you care if you want to test that your program has indeed written something
ls -gtr ~/public/imasdb/test/3/mdsplus/0
- test - machine name
- 3 - IMAS version (major)
- 0 - Additional folder level to store RUN numbers beyond 10000

The file names are:
- ids_PulseRun.tree
- ids_PulseRun.datafile
- ids_PulseRun.characteristics
Where Pulse is the pulse number and Run is the 4 rightmost digits of the run number of the Data Entry.
Example: PULSE 22, RUN 2 consists of 3 files:
- ids_220002.tree
- ids_220002.datafile
- ids_220002.characteristics

Data Dictionary Lifecycle

An IMAS DD version is defined by 3 levels of revisions named M.N.i (Major.Minor.Micro) : example 3.16.0
The degree of evolution flexibility depends of the lifecycle status of the considered part of the DD:
- “Alpha” parts of the DD may freely evolve (through micro revisions)
- “Active” parts of the DD may only evolve through backward compatible changes (minor revision) – or trigger a major revision
- “Obsolescent” parts of the DD are kept for temporary backward compatibility of modules but might not exist in the next major revision
JIRA trackers / GIT pull requests provide an effective way to ask for DD evolutions and public release of a new DD version
The IMAS installer provides a mechanism to install and work with any private development branch of the DD

This introduction presented the IMAS basic concepts and some details on the ITER Physics Data Model
Other training sections will guide you for interfacing codes, generating workflow components, running workflows
The Physics Data Model User Guide is the technical reference for using IMAS and the Access Layer. You can find it (and many other information) on https://confluence.iter.org/display/IMP
In case of any question, raise it on https://jira.iter.org