2/10/2000 chep2000 padova italy the babar online databases george zioulas slac for the babar...

2/10/2000 CHEP2000 Padova Italy

The BaBar Online Databases

George Zioulas

SLAC

For the BaBar Computing Group


Overview

• Introduction• Selection criteria• Domains

– Conditions

– Ambient

– Configuration

• Operational experience and future plans• Summary


Introduction

• BaBar has adopted an object oriented approach for its offline and online software

• OODBMS was selected for the event store• Objectivity/DB is the underlying technology• The Online Databases provide storage for non-

event data • Requirements:

– Reliability

– Fast storage and retrieval of data; storage of several TB


Selection Criteria

• Support of object oriented design. C++ interface

• Hierarchical structure provides logical storage through persistent objects, databases and federations

• Application-side caching of objects retrieved from the database improves performance

• Autonomous partitioning and fault tolerance

• Distributed architecture and scalability

• Reuse of existing code developed by the offline system

• Common tools for administration, maintenance and data distribution


Conditions Database

• Manages and tracks the Conditions of the experiment– Offline: detector calibrations, alignment etc.

– Online: run information, electronic calibrations, fast monitoring

• Hierarchical structure

• Data indexed on time key

• Data versioning


Ambient Database

• Provides the storage of ambient data from the Detector Controls system

• Design similar to Conditions Database• No versioning of objects• Operational information:

– 27 archiving processes write about 100 objects once per hour

– Total size of objects about 3 MB

– Storing time about 1min


Ambient Data Access

AmbientDatabase

AmbientServer

(C++/CORBA)

JavaBrowser

JavaBrowser


Configuration Database

• Provides storage for the configuring parameters of the online system

• Interface to Dataflow ROMs (VxWorks) via UNIX server

• Configuration objects indexed on numeric keys

• Hierarchical tree-like structure

• Tree provides navigation from top, indexed by configuration key, to the subsystem configuration data on the leaves of the tree

• Simplifies system partitioning. Allows authorization control on subsystem level


Configuration Trees

A lia sP h ys ics

D a taK e y: 1 07

F ile IDK e y: 1 04

C h ip sC o n figK e y: 1 03

D a taK e y: 8

F ile IDK e y: 8

R u n C o n figK e y: 10

S vtK e y: 1 78

D ch C a lC yc le sK e y: 79

D chK e y: 88

C o m p P ro xy 1K e y: 2

C o m p P ro xy 2K e y: 2

D e tC o n tK e y: 2

D a taK e y: 63

E m cK e y: 73

T opK e y: 6 54


Configuration Database

• Processes accessing the database with each configure transition:– 32 Event Processing nodes

– 17 Detector Control processes

– Dataflow server

• Configuration time about 15 sec


Production Federation

Event storePR relatedConditions

Configuration

ConditionsAmbient

Configuration

Prompt Reco Federation Online Federation

Now

Event storePR related

ConditionsAmbient

Configuration

Production Federation

Comp. Building (SCS) Interaction Hall (IR2)

Online PartitionPrompt Reco Partition

May 99


Operational Experience

• Running Objectivity 5.2. Many reads or one write mode

• System is reliable. A few hours of downtime for maintenance, upgrades

• 56 GB of non-event data have been recorded since May 1999

• Soon to start archiving FM histograms (1GB/day)

• Developed own schema evolution

• Concurrency problems. Read locks prevent processes from writing data

• Sweeps between federations are tedious, time consuming


Future plans

• Merge back the Online and Prompt Reconstruction federations

• Deploy the federation partitioning and fault tolerance

• Improve the user interface of database browsers and servers


Summary

• The BaBar Online Databases are in use since May 1999

• Problems during commissioning have been fixed• System performance has been good and reliable• Downtime mostly due to maintenance and

upgrades• Work on operational issues under way

2/10/2000 chep2000 padova italy the babar online databases george zioulas slac for the babar...

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