# Finding data in the Bookkeeping

<!-- contributors:start -->
:::{admonition} Page contributors
:class: callout dropdown

Valentin Volkl, Juraj Smiesko, Clement Helsens, Gerardo Ganis
:::
<!-- contributors:end -->

Knowing how data flows through the various Gaudi applications is crucial for
knowing where to look for your data.

Data are catalogued in ‘the bookkeeping’, and are initially sorted in broad
groups such as 'Delphes Events', ‘Full detector simulation’, and according to the FCC flavor (ee, hh or eh).
After this, a tree of various application and processing versions will
eventually lead to the data you need.

:::{admonition} Learning Objectives
:class: objectives

* Find FCC data in the central storage
* Store FCC data in the central storage
:::

## Obtaining access permissions

In general, access to the EOS shared filesystem is obtained by subscribing to the relevant egroups [here](https://e-groups.cern.ch/e-groups/EgroupsSearchForm.do).
For running the tutorials read access is sufficient, which is granted through subscription to the following e-group:
```
fcc-eos-access
```
which is open for self subscription requests.

For analysis activities, the physics groups have dedicated areas under `/eos/experiment/fcc/ee/analyses_storage/`
```
/eos/experiment/fcc/ee/analyses_storage/BSM
/eos/experiment/fcc/ee/analyses_storage/EW_and_QCD
/eos/experiment/fcc/ee/analyses_storage/flavour
/eos/experiment/fcc/ee/analyses_storage/Higgs_and_TOP
```
Write access to those areas is controlled by dedicated e-groups
```
fcc-eos-write-ee-analyses-bsm
fcc-eos-write-ee-analyses-ew-qcd
fcc-eos-write-ee-analyses-flavor
fcc-eos-write-ee-analyses-higgs-top
```
managed by the conveners of those physics groups, which should be contacted for subscription.

See the [here](https://hep-fcc.github.io/FCCSW/computing/) for more information about FCC computing resources.

## Finding Data

Browse the fcc directory on `eos`, the shared filesystem used by CERN.

```bash
tree /eos/experiment/fcc/ -L 2
```

You should see an output similar to:

```
/eos/experiment/fcc/
├── ee
│   ├── accelerator
│   ├── analyses
│   ├── datasets
│   ├── generation
│   ├── mdi
│   ├── simulation
│   ├── tutorial
│   └── utils
├── eh
│   └── datasets
├── helhc
│   ├── analyses
│   ├── generation
│   ├── utils
│   └── YR_summary
├── hh
│   ├── analyses
│   ├── CDR_script
│   ├── generation
│   ├── hcal
│   ├── simulation
│   ├── tests
│   ├── testsamples
│   ├── tutorials
│   └── utils
```

The file paths on eos already give an indication where to find what kind of data. In some instances, the information is very detailed:

```bash

ls /eos/experiment/fcc/ee/tutorial/
```

But not all datasets follow this exact format. In case of questions simply contact the software team.

On lxplus `eos` is mounted as a standard directory and you can use standard bash tools such as `ls`, `cp`, `mv` ... to manipulate the files - Also to write them provided you have the correct permissions.


However, using eos like this is not recommended to transfer actual data (we speak from experience) and also not possible on machines where eos has not been mounted. The right tool here is `xrdcp`, which uses the xrootd protocol. It works like   `cp` (minus some features) but all paths must be prefixed by the URL `root://eospublic.cern.ch/`.