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Objectivity/DB and Oracle - Comparing the Architectures

Objectivity/DB and Oracle - Comparing the Architectures . Dirk Düllmann Comparing the storage hierarchies… Confusing the Terminologies…. Federation. Database. Container. Page. Object. Objectivity/DB Storage Hierarchy. Main architectural limitations result from design choice for OID

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Objectivity/DB and Oracle - Comparing the Architectures

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  1. Objectivity/DB and Oracle- Comparing the Architectures Dirk Düllmann Comparing the storage hierarchies… Confusing the Terminologies…

  2. Federation Database Container Page Object Objectivity/DB Storage Hierarchy • Main architectural limitations result from design choice for OID • 64K databases • 32K containers per database • 64K logical pages per container • 64K object slots per page

  3. “Federation” Oracle Storage Hierarchy Database Table • No (or not yet known) limit on number of databases and tables • 64k partitions • practical limit expected to be lower • Tablespace can be declared offline and transported • 1022 files per tablespace • OS files or raw partitions • 64k files per instance • Is this sufficient? Partition Tablespace File Extend Block Object

  4. Federation • Objectivity:A set of many database files possibly distributed across several data serving hosts • Oracle:A set of many database instances possibly distributed across several hosts

  5. Database • Objectivity: A single operating system file, always part of a federation • Oracle: All data handled by a single server instance • many files locally accessible to one host

  6. Container/Table • Objectivity - Container: • Heterogeneous collection of persistent objects • Physical clustering: objects reside “close” to each other on disk • In practice often rather homogenous (clustering by type) • Oracle - Object Table: • “Homogeneous” collection of persistent objects • Logical collection: objects may spread many files • May become heterogeneous by “substitutability” • Ability to store a derived object in a table of it’s base class • Some similarities, but no 1-to-1 correspondence

  7. Partition • Objectivity:Autonomous part of a federation which is handled by an independent lockserver. • Oracle:Part of a larger table which typically resides on a different tablespace.

  8. Exten{t|d} • Object Databases:Set of all objects of a given class in an Object Database. • Oracle:Element of the lower level storage hierarchy (allocation granule for files)

  9. Block/Page • Objectivity- Page :Unit of disk and network I/Os • same value for whole federation • Oracle - Block:The disk I/O unit (not the unit of exchange between client and server), • may be vary between different tablespaces

  10. Client Side Cache • Objectivity: • Cache contains complete database pages • Persistent objects are located on those pages • Oracle: • Client cache contains individual objects • Persistent objects are constructed from table data (and written back) using (typically) generated conversion methods

  11. Storage Format • Objectivity: • “Native” format short, long, int, float, double • Some padding but otherwise closely related to C++ “in-memory” representation • Oracle: • Programming language independent format “Number” • Inpact on storage overhead, CPU overhead and numeric stability

  12. Summary • Architecture and in storage hierarchies are very different! • Performances and practical limits will differ as well… • IT/DB will perform detailed tests (see Marcins presentation) • Several common terms have very different meanings! • Don’t re-apply your Objectivity mental model to Oracle!

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