Overview of Atlas DB activities

1
Overview of Atlas DB activities

• Recall of Athena/Gaudi architecture
• Recent database developments
• Near-term activities and challenges
• LHC-wide projects on data management
• A common project underway conditions databases
• Transaction Management

2
Recall the architecture of Athena/Gaudi
Data Service
Persistency Service
Requests DataObject
manages
Conversion Service
Persistent Store
DataObj
DataObj
Atlas DB
Cnv
Cnv
Convertor
Algorithm
Transient Store
Converts transient lt-gt persistent
3
Recent database developments

• Access to Physics TDR data from production
  Objectivity database or from Zebra
• Data storage and access in Objectivity of
  user-defined data objects through Athena control
  framework
• packages using this today include ATLAS fast
  simulation, and standard generators (ISAJET,
  PYTHIA, )
• Ability to switch storage technologies at run
  time by changing job options has been
  demonstrated
• Objectivity or ROOT, the latter via generic
  persistence mechanisms
• Associated infrastructure for building database
  software and databases

4
A sampling of near-term activities and challenges

• Database architecture document--for review by
  collaboration late this summer
• Database infrastructure to support trigger TDR
• Database infrastructure to support Data Challenge
  0 (complete simulation/reconstruction/analysis
  chain December 2001)
• Data Challenge 1 (beginning in 2002), in which
  data volume and data distribution begin to
  matter, will be used to evaluate our database
  architecture, as well as the technology in which
  it is implemented
• Technology evaluations are expected to involve at
  least Objectivity and ROOT

5
Near-term activities, cont.

• Data dictionary effort well underway (supports
  automatic generation of persistent
  representations and converters)

6
LHC-wide projects on data management

• When we have 5 petabytes of data in 1,000,000
  5-gigabyte files, how much of our storage
  management problem will depend on whether those
  files are ROOT files or Objectivity databases or
  ordinary ASCII files?
• We are eager to participate in LHC-wide common
  projects to address issues of storage management
  (tertiary storage, Tier 0 infrastructure,
  infrastructure for distribution to Tier 1s, ),
  even if persistence technologies vary from
  experiment to experiment.

7
A common project underway conditions databases

• CERN IT Division is developing a timestamp-based
  retrieval database for time-varying conditions
  data, to be implemented in Objectivity and in
  Oracle
• Many development releases first production
  release was on 1 June 2001
• ATLAS has been contributing requirements and
  evaluation, and currently plans to use this
  technology, connecting it to our control
  framework in the coming months
• another collaborative effort (between LHCb and
  ATLAS) will provide common Gaudi/ATHENA services
  for access to this IT-developed database
  infrastructure

8
Transaction Management

• Working with the ConditionsDB made clear the need
  for decoupling of domains working with Objy
• Using HepDbApplication (ooSession) from HepODBMS
  allows only a single transaction for multiple
  domains - a second startUpdate can only be really
  committed when the first commit has occurred.
• Objy allows multiple independent transactions to
  coexist within separate contexts
• We are currently looking at BaBars transaction
  management and plan to profit from their
  experience
• Simon Patton described the use of BdbDomain which
  allows activation/deactivation and multiple
  (mini)transactions

9
Transaction Management, cont.

• We need to coordinate transaction management with
  the ConditionsDB
• Various possibilities
• Minimal model ConditionsDB works entirely within
  its own context
• At each action, ConditionsDB saves the current
  context, sets its own context as current and when
  finished it restores back the original context
• Maximal model work together to redo
  HepDbApplication allowing for the use of
  ooContexts