Bernhard Düchting Principal Sales Consultant BU Database - Migration Oracle Germany

Migrating C++ Applications using OCCI

Agenda  Object Orientation and C++  Oracle C++ Call Interface - Overview  Objects Access  Summary  Case Study - Using OCCI at CERN  Q & A

Object Orientation with 9i  Native data types for collections  Definition of object types, object tables and object views  Explicit table inheritance using SQL-99  Implicit inheritance using references (REF)  Overloading of object methods  Online schema evolution

Object Orientation and C++  Header files with object definition generated from object schema  No need for separate object-relational mapping  Object cache with pre-fetch capability for transient and persistent object management  Server-side object locking

Steps for Migration  Determine object model and class hierarchy  Use JDeveloper 9i to map to Oracle object schema  Generate C++ header files using Oracle Type Translater (OTT)  Modify old C++ access classes as required to work with new object type definitions  Add functionality for transient and persistent object management as required

OCCI Partners and Customers  A major GIS cartridge partner – High performance object-relational and spatial data access for national surveying system  A global power transmission manufacturer – Handle complex object-retrieval for graphical maintenance console  A global medical systems manufacturer – Replace ODBMS to manage patient image data  A national postal authority – Replacing third-party persistency framework

Agenda  Object Orientation and C++  Oracle C++ Call Interface - Overview  Objects Access  Summary  Case Study - Using OCCI at CERN  Q & A

Oracle C++ Call Interface OCCI  Built on OCI – Similar control and performance of OCI  Based on Standards – ANSI/ISO C++ Standard, including STL – Associative access API design similar to JDBC  Performance – Prefetching, client-side cache, array operations, data buffering, thread safe  API easy to use – API design consistent with C++ programming paradigm (e.g. new operator overloaded for creating persistent objects)

OCCI Basics  Setup of Environment and Connection  Executing SQL Statement – SQL statement – Prepared SQL statement with bind variables – Stored procedure  Executing SQL Query – Return multiple rows into result set – Use prefetching for performance  Seamless support of Oracle datatypes – varchar2 mapped to string, – collection mapped to vector STL

OCCI Advanced Features  Connection Pooling – Improves scalability by multiplexing many logical connections over few physical connections – Optimal usage of physical connection resource – Connection pool shrinks and grows on demand  Thread Safety – OCCI handles mutexed access to shared resources  Array Operations – Insert/update multiple rows – Fetch multiple rows in one round-trip

Environment *env=Environment::createEnvironment(Environment::OBJECT); RegisterMappings(env); Connection *conn=env->createConnection(“scott”,”tiger”,””); Statement *stmt=conn->createStatement(); ResultSet *resultSet=stmt->executeQuery(“select ref(t) from atable t where n=0”); if (ResultSet::DATA_AVAILABLE == resultSet->next()) { Ref ref=resultSet->getRef(1); } conn->commit(); stmt->closeResultSet(resultSet); conn->terminateConnection(conn); Environment::terminateEnvironment(env); create/modify/delete objects Example Session

Agenda  Object Orientation and C++  Oracle C++ Call Interface - Overview  Objects Access  Summary  Case Study - Using OCCI at CERN  Q & A

OCCI Object Features  Transparent access of database objects as C++ instances  Navigation of objects as simple as de- referencing smart-pointers  Client-side caching of C++ objects  Supports all 9i object features including inheritance  Oracle Type Translator (OTT) – Maps object types to C++ interface classes

Client-side Object Cache  Memory Buffer for Objects – Transparent lookup and memory management support – Stores and tracks objects fetched from server to client side – Maintains references – Created when OCCI environment is initialized in object mode  Benefits – Reduces client/server round-trips – Object-level locking

Accessing Objects  Unique Object Identifier OID  Navigational Interface – No SQL – Navigate using object references (REF) – Create/access/lock/delete/flush/commit  Associative Interface – Use SQL or PL/SQL – Data buffers, no cost of transporting data to client

Representing Objects CREATE TYPE ADDRESS AS OBJECT ( state CHAR(2), zip CHAR(2));  OTT generates: class ADDRESS : public PObject { // OCCI pre-defined class protected : string state; string zip; public : void *operator new(size_t size); // create a transient instance void *operator new(size_t size, Connection *conn, string& table); // create a persistent instance }

Working with Objects I  Create new object – Use new operator – Transient or persistent objects  Fetch object from server – Pin object in cache using REF – Fetch object by value  Navigate to object – Use pinned object to traverse hierarchy – Only with referenceable objects

Working with Objects II  Modify object – Make changes in C++ application – Mark persistent object as dirty  Flush changes to server  Commit transaction – Includes flushing dirty objects

Oracle Object Cache REF Client side cache Server buffer cache Pin Network flush load

Agenda  Object Orientation and C++  Oracle C++ Call Interface - Overview  Objects Access  Summary  Case Study - Using OCCI at CERN  Q & A

Summary I  Oracle C++ Call Interface OCCI – Simple and easy – High-performance and Scalable API – Comprehensive support of Oracle Database features – Ideal choice for implementing high performance mid-tier applications – 9i Release 2 focus on performance

Summary II  Easy migration of C++ applications – Determine UML class model – Import into Jdeveloper 9i – Re-model as required – Generate Oracle 9i object schema – Generate C++ header files with OTT – Modify C++ persistency classes as required

Agenda  Object Orientation and C++  Oracle C++ Call Interface - Overview  Objects Access  Summary  Case Study - Using OCCI at CERN  Q & A

C A S E S T U D Y Using OCCI at CERN

Overview  Brief introduction to CERN & LHC – Huge data volumes, long lifetime, Use of OO  Extensive experience with databases – Oracle since 1982; ODBMS since 1995  Migration of existing applications – Complex C++ programs; – Up to 1000 classes; – Many KLOC - MLOC

CERN – European Organization for Nuclear Research

The LHC Machine

RAWRAW ESDESD AODAOD TAG random seq. 1PB/yr (1PB/s prior to reduction!) 100TB/yr 10TB/yr 1TB/yr Data Users Tier0 Tier1

Overview  Brief introduction to CERN & LHC – Huge data volumes, long lifetime, OO  Extensive experience with databases – Oracle since 1982; ODBMS since 1995  Migration of existing applications – Complex C++ programs; – Up to 1000 classes; – Many KLOC - MLOC

CERN & Databases  Oracle brought in for construction of previous accelerator – 1982; LEP – 27km ring 100m underground – Now pervasive through-out work of lab  Early 1990s: move to object orientated approach for “physics applications” – Extensive experience with Object Databases – Until end 2001, baseline choice for multi-PB requirements of LHC – Production experience with ODBMS up to ~100TB  cf SLAC/BaBar 500TB system  Requirement for LHC: 100PB system (all data)

Overview  Brief introduction to CERN & LHC – Huge data volumes, long lifetime, OO  Extensive experience with databases – Oracle since 1982; ODBMS since 1995  Migration of existing applications – Complex C++ programs; – Up to 1000 classes; – Many KLOC – MLOC – Exploit associative and navigational access

OCCI / OTT Functionality  CERN has worked closely with Oracle since prior to Oracle 9i announcement on OCCI/OTT functionality, interfaces, implementation etc  Active partner in 9iR1 & 9iR2 Beta program  Happy to confirm that required functionality & product stability are available in 9iR2

Migration of Existing Apps (I)  Detector Conditions Database – Previously implemented on ODBMS – Same user interface re-implemented using OCCI  Client based on associative access No changes to user code! (Except connect string) – Complete re-design of underlying data model  Implemented using pure relational model Uses partitioned tables; materialized views; stored procedures; indexes; … – One of several applications for production 9iRAC service being setup at CERN  Other similar applications foreseen – Grid replica catalogue, production control DB, …

Migration of Existing Apps (II)  Take existing large C++ application  Strip out ODBMS-based persistency layer  Replace with OCCI using navigational access  Strong requirements from both user & developer point of view:  C++ Developer: – No change to object model & classes  User: – No change to application

CMS Offline Software – its big!

Functionality tests (I) Tests of basic components Simple objects Compound objects – Contain other user types as attributes Inheritance Composition by reference Collections by value & reference (II) Full object models Exploits all above features Stresses client-side object cache & navigation

CMS Migration  Independent module developed to handle DB interface – Oracle or ODBMS  Modification of the application and the implementation of the independent module totaled several hundreds of lines of code No other code was modified! From user application level … users are not aware of the change

Conclusions  OCCI offers powerful persistency mechanisms for C++ applications – Both associative & navigational access supported  Full power of database still available – Significant benefit over conventional ODBMS  Migration of complex applications proven – Achieved with no change to user code

A Q & Q U E S T I O N S A N S W E R S