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The Design and Implementation of the STAR Tag Data Base

The Design and Implementation of the STAR Tag Data Base. D. Zimmerman Lawrence Berkeley National Lab CHEP ‘98 Mass Storage and Data Management #516. Objective of Tagdb:. Outline. Efficient Access to interesting events Minimize the need to interact with events which are not of

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The Design and Implementation of the STAR Tag Data Base

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  1. The Design and Implementation of the STAR Tag Data Base D. Zimmerman Lawrence Berkeley National Lab CHEP ‘98 Mass Storage and Data Management #516

  2. Objective of Tagdb: Outline Efficient Access to interesting events Minimize the need to interact with events which are not of interest (to this analysis) Reduce the biases arising from rigid separation of events by analysis stream • Star Event Model • Tag Data Base, what and why • Life Cycle of the Tag • MDC1 plans September 2, 1998 CHEP 98 Star Tag Data Base

  3. STAR Experiment at RHIC • Heavy Ion Experiment at RHIC • Nominal Running Au+Au at 200 GeV/A • ~400 Physicists • First Physics Run Autumn 1999 September 2, 1998 CHEP 98 Star Tag Data Base

  4. 107Events/nominal year Large ~20 MByte events Complex (multi-component) events Distribution through secondary and tertiary storage at RCF Wide range of access patterns Objectivity based Event components clustered by type Grand Challenge Architecture (GCA) data mining Data Model in Star September 2, 1998 CHEP 98 Star Tag Data Base

  5. Star DST Event Structure September 2, 1998 CHEP 98 Star Tag Data Base

  6. Tag Data Base • Tags are navigation tools • Selectively allows fast access to interesting events • Facilitates cross analysis stream communication • Star has many diverse analysis streams with large overlap • Tags are disk resident event components • Objectivity persistent objects • Tag data accumulates from each stage of (re)processing • Tags and QA information grows as the event undergoes each stage of (re)processing September 2, 1998 CHEP 98 Star Tag Data Base

  7. Tags - Events • All event Header objects and tag objects are disk resident. • Separate data bases (files) for Tags and EvHdrs • Each experiment run corresponds to a new container in the event and tag header data bases. • The tags associated with a particular production for a run are stored in distinct containers within the tag database Examples of data members for the Tag Object: Online Tags: trigger_mask, run#, L0_trigger flag, L1 trig word Production Tags: Total Good Tracks, #Pile Up Vertices, # V0s loose cuts, # V0 hard cuts Strangeness Tags: # Lambda+, # Lambda-, # Kaons EbyE Tags: Event Temperature, SCA coefficients September 2, 1998 CHEP 98 Star Tag Data Base

  8. Three principal analysis routes via the Tagdb Objectivity Analysis Tag analysis retrieves event header references. Event components must be on disk GCA Based Analysis (See D. Olson’s talk) Tag is used to build Index for GCA Query Estimator Event reference lists (collections) Passed as a collection to the GCA Data Access through the Tag September 2, 1998 CHEP 98 Star Tag Data Base

  9. Selection of Tagged Events While (TagItr.next()) { \\ Loop over the Tag database TagsCounted++; d_Long number_positive_pions = TagItr->GetLong(‘num_Pion_+’); d_Long number_negative_pions = TagItr->GetLong(‘num_Pion_-’); Pion_Sum = number_positive_pions + number_negative_pions; if(Pion_Sum > Threshold) { TagItr->GetEventRef(EvRef); winners.insert_element(EvRef); } } winners is list of event references which can be used to retrieve event components of interest September 2, 1998 CHEP 98 Star Tag Data Base

  10. Star Event Federation Structure • Event Hdr Dbase Permanently on disk • Container in evthdr dbase = Run • Event Components live on disk as well as HPSS • Based on access patterns • MicroDST information disk resident • Hits archived in HPSS • TagDbase TagHeader Container Each Header has references to Event Hdr and Tags QATag Container QATag Information with version information for Tag Components Tag Information Container eg (DST, uDST, Online, Trigger, Physics Working Groups Each Tag type inherits from StarTag Class General Tag Get and Set methods defined in StarTag class September 2, 1998 CHEP 98 Star Tag Data Base

  11. The Tags for an event correspond to Tag+QATag • Each Event has an event header object • Two uni-directional associations between Tag Header and Event Header Each Tag component pairs with its QATag • Each Tag component pairs with its QATag • QATag contains meta-data for tag Tags QA Tag contains Calibration information for the Associated Tags. Superceded versions of Tags are available for archival in tertiary storage. Production status and quality information (eg CPU time, production machine, prod status).. September 2, 1998 CHEP 98 Star Tag Data Base

  12. Life Cycle of Tag Data Base • The Tags for each event grows as the event structure • builds up. • The processing of each run is atomic. Access to current processing stage is restricted. September 2, 1998 CHEP 98 Star Tag Data Base

  13. Run Header Collection • Run Header contains Varrays of references to EvtHdrs and TagHdrs. • Run Header inherits from the StarCollection class September 2, 1998 CHEP 98 Star Tag Data Base

  14. Personal Event Collections • Physicists build collections based on earlier analysis. • The personal event collection contains associations to their own lists of tag which reside in their Private data base September 2, 1998 CHEP 98 Star Tag Data Base

  15. Adding Tags to the Tagdb • Baseline Schema is laid out on importation to • objectivity • Pre-specified schema is created when the data base is created • Additional tags are added or updated to the schema • as needed during the analysis phase • At the request of physics analysis groups new • tags can be added or updated to the federation schema • Tag information is updated as the event becomes • more refined. QATags maintain version information • Tag Access methods are used to build more • sophisticated indices/queries from tag data members • (e.g. ratio of charged to neutral pions as tag) • DCC Signal = (PionPos+PionNeg)/PionNeut September 2, 1998 CHEP 98 Star Tag Data Base

  16. MDC1 Plans for the Tagdb • Baseline tags will be created when the event is first read into objectivity. The tags will be filled as the event grows • Additional tags be added to events at the request of the Physics Working Groups • Individual physicists will copy the tag data base in order to build up event collection lists as well as to study the selection process • Test the event structure for performance and robustness • Learn how (not) to break the federation under field conditions • evaluate different schemes for re-tagging events. • Private collection tags • Tag versioning • Generic tags September 2, 1998 CHEP 98 Star Tag Data Base

  17. Tags - Events • The tag objects for each event present simple schema for efficient querying. • Tag is disk resident • compact • available for copying offsite for analysis or collection development • Analysis makes selection based on Tag information to pick out events of interest September 2, 1998 CHEP 98 Star Tag Data Base

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