1. Offline framework for conditions data
L.Betev
TPC commissioning meeting
Geneva, February 17, 2006

2. Outline Conditions data in Offline Content and access
Status of offline framework and plans

3. Conditions DB relations in ALICE
Conditions data in Offline
Conditions data are stored and accessible by the applications on the GRID
Treating all source databases as potentially containing conditions information and as “closed”, i.e. only accessible at CERN
It would be difficult to provide access methods to all DBs from the production and analysis code
The conditions DB framework is providing access methods to all external DBs
Conditions data stored as read only ROOT files:
Object store technology already incorporated in the ALICE offline

4. Conditions DB relations in ALICE (2)
Conditions data access in a Grid distributed production and analysis environment:
The root files are registered in the Grid Distributed File Catalogue:
No need for distributed DBMS in a traditional sense and with all accompanying problems (remote access, replication, authentication, load) – a very big plus
Assures worldwide access to all files and associated tags
Drawbacks:
Replication of information – potentially large parts of ‘external’ DBs have to be put in the offline conditions DB
However the same is true for all LHC experiments

5. External sources of conditions data and relations to offline
DAQ
Trigger
DCS
ECS
Physics data
DCDB
GRID FC:
metadata
file store
calibration procedures
calibration files
AliRoot
Calibration classes
API
files
HLT

6. Conditions DB – content and access
Update frequency:
The condition DB will have rather infrequent updates (max: once per run)
The objects themselves can have rich internal structure with finer granularity, depending on the detector calibration / alignment needs
Access framework:
Simple user interface and data identification (strings)
Automatically get the right valid object
Modification of the objects is handled through versioning
Same interface for different types of data sources (local file, Grid)

7. Data organisation - simple filesystem-like storage:
Calibration/DETECTOR/FirstRun-LastRun.version

8. Status of the access framework
AliRoot implementation:
Classes to put/get conditions objects are ready and tested by all ALICE detector groups
Access methods:
GRID file and metadata storage (AliEn GRID File catalogue) – deployed
Conditions data dump in local files - expert use, new versions of conditions, ‘disconnected from the GRID’ mode – deployed
Combination of the above - deployed

9. Status of the access framework (2)
Current issues:
Availability of conditions data
‘Quasi-online’ first pass reconstruction – good enough version of the conditions data should be available almost immediately
Who provides what: offline is a pure consumer of conditions data – should make sure that the methods and procedures exist to store the data in the relevant ‘external’ DBs
APIs to external sources
Access to some of the DBs not solved yet (especially LHC machine information)

10. Conditions DB – automatic information gathering
Automated system – Shuttle:
Collecting conditions data
from external DB at predetermined
time intervals (for example at
the end of every run)
Processing collected data
using detector-specific preprocessor
Storing conditions data in
the Conditions DB

11. Conditions DB – information gathering (2)
Similar systems can be used to process conditions data from other sources:
Only new interfaces needed
The processing of the data is done in AliRoot (no change of framework)
Allows detector groups to do analysis and reduction of the raw data volume before storing it in the Conditions DB
The Shuttle program access to DCS and DAQ DBs is deployed and tested:
Real life test (Summer 2006) running with detector data – ALICE TPC cosmic ray tests

12. Summary on status and plans
GRID/ROOT based Conditions DB framework ready
Implementation in detector reconstruction and analysis code ongoing
Automatic gathering of conditions data from external sources – prototype ready
Tests with real detector data – Sumer 2006
Continuous tests ‘on the GRID’ as part of the ALICE PDC’06/LCG SC4
Current issues
Availability of conditions data to offline from external sources
‘good enough’ conditions data available for the first round of ‘quasi-online’ processing

13. Status of TPC