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OLE DB
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OLE DB (Object Linking and Embedding, Database, sometimes written as OLEDB or OLE-DB) is an API designed by Microsoft that allows accessing data from a variety of sources in a uniform manner.[1][2] The API provides a set of interfaces implemented using the Component Object Model (COM); it is otherwise unrelated to OLE. Microsoft originally intended OLE DB as a higher-level replacement for, and successor to, ODBC, extending its feature set to support a wider variety of non-relational databases, such as object databases and spreadsheets that do not necessarily implement.
Methodology
[edit]OLE DB separates the data store from the application that needs access to it through a set of abstractions that include the datasource, session, command, and rowsets. This was done because different applications need access to different types and sources of data, and do not necessarily want to know how to access functionality with technology-specific methods. OLE DB is conceptually divided into consumers and providers. The consumers are the applications that need access to the data, and the providers are the software components that implement the interface and thereby provides the data to the consumer. OLE DB is part of the Microsoft Data Access Components (MDAC).
Support status
[edit]Microsoft's release of SQL Server 2012 (internal code: 'Denali') is the last to include an OLE DB provider for SQL Server, but support will continue for 7 years.[3] According to a related Microsoft FAQ,[4] "Providers like ADO.NET which can run on top of OLE DB will not support OLE DB once the latter is deprecated", but the same answer in the FAQ states that the original post relates only to the OLE DB provider for SQL Server, so the position of OLE DB itself remains unclear. The same FAQ states that ODBC performs better than OLE DB in most cases.
However, during subsequent reviews it was determined that deprecation was a mistake because substantial scenarios within SQL Server still depend on OLE DB and changing those would break some existing customer scenarios. On Oct 6, 2017 Microsoft announced that OLE DB was undeprecated, and a new version to maintain dependencies would be released in early 2018.[5]
OLE DB providers
[edit]An OLE DB provider is a software component that enables an OLE DB consumer to interact with a data source. OLE DB providers are analogous to ODBC drivers, JDBC drivers, and ADO.NET data providers.
OLE DB providers can be created to access such simple data stores as a text file and spreadsheet, through to such complex databases as Oracle, Microsoft SQL Server, Sybase ASE, and many others. It can also provide access to hierarchical data stores such as email systems.
However, because different data store technologies can have different capabilities, every OLE DB provider cannot implement every possible interface available in the OLE DB standard. The capabilities that are available are implemented through the use of COM objects; an OLE DB provider will map the data store technologies functionality to a particular COM interface. Microsoft describes the availability of an interface as "provider-specific," as it may not be applicable depending on the data store technology involved. Providers may augment the capabilities of a data store; these capabilities are known as services in Microsoft parlance.
References
[edit]- ^ Foxall, James D. (2000). MCSD in a Nutshell: The Visual Basic Exams. "O'Reilly Media, Inc.". p. 259. ISBN 978-1-56592-752-0.
- ^ Agarwal, Vidya Vrat; Huddleston, James (June 17, 2008). Beginning VB 2008 Databases: From Novice to Professional. Apress. p. 154. ISBN 978-1-4302-0560-9.
- ^ Microsoft SQLNCli team blog: Microsoft is Aligning with ODBC for Native Relational Data Access
- ^ SQL Server Forums - SQL Server Data Access: Microsoft is Aligning with ODBC for Native Relational Data Access
- ^ Microsoft SQLNCli team blog: Announcing the new release of OLE DB Driver for SQL Server
- "OLE DB Providers Overview". Microsoft. MSDN: Data Developer Center. Retrieved March 23, 2011.
OLE DB
View on GrokipediaIntroduction
Definition and Purpose
OLE DB is a high-performance, Component Object Model (COM)-based database technology designed to provide applications with a uniform method for accessing data stored in diverse formats and locations. It consists of a set of COM interfaces that enable interaction with a wide array of data sources, including relational databases, non-relational stores such as spreadsheets and object databases, and hierarchical data structures. This approach allows developers to treat varied data repositories as tabular or rowset-based entities, abstracting away the underlying storage differences.[3][5][6] The core purpose of OLE DB is to deliver a vendor-neutral and extensible framework for data consumers—such as applications or middleware—to connect and query data providers without writing source-specific code. Unlike ODBC, which primarily targets relational databases through SQL-based access, OLE DB broadens this scope to support non-relational and semi-structured data, facilitating seamless integration across heterogeneous environments. This design promotes scalability and adaptability in data-driven applications by standardizing access patterns while accommodating custom extensions through its COM foundation.[3][7] Key benefits of OLE DB include its uniform access model, which reduces development complexity by providing consistent interfaces regardless of data source type; support for complex data types, including binary large objects (BLOBs) and structured objects via COM; and deep integration with the Windows operating system ecosystem through COM, enabling efficient, high-performance data operations in native applications. OLE DB was announced in 1996 as a cornerstone of Microsoft's unified data access strategy, combining with ActiveX Data Objects (ADO) to streamline data connectivity across enterprise systems.[3][8]History and Development
OLE DB was developed by Microsoft in late 1996 as a successor to earlier data access technologies such as Open Database Connectivity (ODBC), Data Access Objects (DAO), and Remote Data Objects (RDO), with the goal of establishing a Component Object Model (COM)-based universal data access layer that could provide uniform access to diverse data sources beyond traditional relational databases.[8][9] The initiative built upon ODBC's SQL-focused interface while extending support to non-relational data like mainframes, desktop files, and Internet resources, aiming to enhance interoperability across enterprise environments. The OLE DB Software Development Kit (SDK) version 1.0 was made available on September 3, 1996, marking the formal introduction of these COM interfaces for developers.[8] OLE DB was first integrated into Microsoft Data Access Components (MDAC) starting with version 1.0 in August 1996. It saw significant enhancements with version 2.0 integrated into MDAC in summer 1998, introducing greater maturity and extensions like OLE DB for Online Analytical Processing (OLAP) to handle multidimensional data.[10] By 2000, OLE DB evolved further with enhanced support for XML and web data integration, particularly through its role in SQL Server 2000, which enabled XML querying over HTTP and data manipulation in browser-based applications via OLE DB providers.[11] This version remained included in SQL Server releases up to 2012, supporting features like the SQLOLEDB provider for native connectivity.[2] Key milestones included a planned deprecation announcement in August 2011, when Microsoft aligned native relational data access toward ODBC for SQL Server releases starting with code name "Denali" (SQL Server 2012), citing OLE DB's limitations in modern scenarios while committing to seven years of support.[12] However, due to significant dependencies in SQL Server ecosystems, Microsoft reversed this decision on October 6, 2017, undeprecating OLE DB and releasing the new Microsoft OLE DB Driver for SQL Server (MSOLEDBSQL) in early 2018 to maintain backward compatibility and add features like multi-subnet failover and TLS 1.2 support.[13] As of 2025, MSOLEDBSQL continues to be actively maintained, with version 19.4.1 released in May 2025, supporting modern features such as Always Encrypted and Azure Active Directory authentication. This shift reflected broader influences from Microsoft's transition to .NET technologies, where ADO.NET emerged as the primary data access framework for managed code, positioning OLE DB as an underlying enabler for legacy and native applications.[14][15]Architecture
Core Components
OLE DB's architecture is built upon the Component Object Model (COM), enabling high levels of interoperability among diverse data sources and applications by standardizing data access through a set of interfaces. This design promotes a layered model that separates the physical data storage from the logic used to access and manipulate it, allowing for flexible integration in multi-tier environments without relying on traditional client-server paradigms. In this model, data is typically exposed in a tabular format, facilitating uniform handling regardless of the underlying source, such as relational databases or flat files.[16] At the core of this architecture are consumers and providers. Consumers are applications, middleware, or system components that initiate data access requests by invoking methods on OLE DB interfaces to retrieve, update, or manage data. Examples include business applications like Microsoft Office tools or custom software that query data sources for reporting purposes. Providers, in contrast, are COM-based software components that implement these interfaces to encapsulate and expose data from specific sources, translating native data formats into the standardized OLE DB structure for consumers. For instance, a provider for a relational database might handle SQL queries, while a file-based provider could expose spreadsheet data as rowsets. This provider-consumer interaction ensures that consumers remain agnostic to the data source's specifics, enhancing portability and scalability.[16] Service components further support the architecture by providing auxiliary functionality that bridges consumers and providers. Enumerators facilitate the discovery and instantiation of available providers by scanning system registries or configurations to list compatible components for a given data source. Error objects, extensions of COM automation error mechanisms, allow providers and other components to return detailed error information, including descriptions and help contexts, enabling robust error handling across the system. Additionally, service providers act as intermediaries that enhance data access without owning the data themselves; they consume from underlying providers and produce augmented outputs, such as through cursor services for result set navigation or data shaping for hierarchical views. These components collectively ensure reliable discovery, error management, and extended capabilities in the OLE DB ecosystem.[17])[17] The runtime environment for OLE DB is provided by Microsoft Data Access Components (MDAC), which supplies foundational services to streamline operations. MDAC includes OLE DB core services that manage resource efficiency, notably through automatic connection pooling, where data source connections are cached and reused to minimize overhead in high-frequency access scenarios. By invoking these services—typically via interfaces like IDataInitialize—applications can leverage pooling without custom implementation, supporting features such as session persistence and transaction enlistment. This integration abstracts low-level details, allowing consumers to focus on data logic while MDAC handles the underlying COM-based orchestration. Consumers interact with provider abstractions like data sources and rowsets through this environment to execute operations efficiently.[18]Data Access Model
The OLE DB data access model is structured around a hierarchy of abstract objects that enable consumers to connect to and interact with diverse data sources in a uniform manner. The foundational abstraction is the data source object, which handles initialization, connection management, and property configuration, including authentication details, to establish a link to the underlying data store such as a database or file system.[19] From this object, sessions are created to scope operations within the data source, allowing for managed interactions like query execution and transaction handling while providing access to metadata about the data structure.[19] Commands represent executable units, typically text-based instructions such as SQL statements, which are processed to retrieve or manipulate data.[19] Finally, rowsets serve as the primary mechanism for presenting and navigating tabular data, supporting operations like scrolling through rows, updating records, and binding columns to consumer variables for access.[19] The typical access flow begins with the consumer initializing a data source object to connect to the target data store, specifying necessary properties and credentials.[19] Once connected, the consumer creates a session from the data source object to define the operational context.[19] Within this session, a command is prepared and executed—often a query like a SELECT statement—which generates one or more rowsets containing the results.[19] The consumer then binds to the rowset's columns and rows to retrieve, navigate, or modify data as needed, ensuring efficient data transfer without direct access to the underlying storage.[19] The model inherently supports advanced features to enhance data handling. Sessions manage transactions that adhere to ACID properties (atomicity, consistency, isolation, and durability), enabling reliable multi-operation sequences across the data source.[19] Schema rowsets, accessible via sessions, provide metadata about database structures, such as tables, columns, and indexes, facilitating informed query construction.[19] Commands can produce multiple result sets in a single execution, allowing efficient retrieval of related data outputs.[19] For extensibility, the model permits providers to implement optional capabilities, such as indexed rowsets for optimized navigation or change notifications to alert cooperating consumers of updates in shared rowsets.[19] Providers play a key role in realizing this model by tailoring the abstractions to specific data sources.[19]Implementation
Providers and Consumers
In OLE DB, providers are COM-based components that expose data sources or services through standardized interfaces, while consumers are applications or components that access those data sources by interacting with the providers. Providers are categorized into data providers, which directly expose tabular data from sources such as relational databases, and service providers, which offer additional functionalities like data shaping or persistence on top of other providers.[17] Consumers rely on these providers to retrieve, manipulate, and store data in a uniform manner, independent of the underlying storage format.[3] Developing an OLE DB provider involves creating a dynamic-link library (DLL) that implements the necessary COM interfaces to expose the data source. Developers must implement mandatory interfaces such as IDBInitialize for initialization and IOpenRowset for accessing rowsets, while optional interfaces like IRowset can be added for enhanced functionality. Property sets, defined through DBPROPSET structures, are used to describe the provider's capabilities, such as supported data types, transaction levels, and cursor models, allowing consumers to query and adapt to the provider's features dynamically. The OLE DB Simple Provider (OSP) Toolkit provides a framework to simplify this process for non-relational or simple data sources, where developers override OSP methods like GetRow or SetData to map application-specific data to OLE DB rowsets, and then register the DLL using Regsvr32.exe along with a custom registration script.[17])[20] Consumers interact with providers by first obtaining the provider's class identifier (CLSID), then instantiating the data source object via the COM function CoCreateInstance, specifying the CLSID and the interface identifier (IID) such as IID_IDBInitialize. Once instantiated, the consumer sets connection properties using IDBProperties::SetProperties, initializes the connection with IDBInitialize::Initialize, and handles errors by checking HRESULT return codes with macros like FAILED. This process enables the consumer to bind to the provider and proceed to execute commands or access data, with the data access abstractions providing a consistent model for rowsets and commands.[21] The following pseudocode illustrates a basic consumer connection sequence:HRESULT hr;
IDBInitialize* pIDBInitialize = NULL;
// Instantiate the data source object
hr = CoCreateInstance(CLSID_MSOLEDBSQL, NULL, CLSCTX_INPROC_SERVER,
IID_IDBInitialize, (void**)&pIDBInitialize);
if (FAILED(hr)) {
// Handle instantiation failure
return;
}
// Set properties (e.g., server, database)
DBPROPSET props = {0};
props.guidPropertySet = DBPROPSET_DBINIT;
props.cProperties = 2;
props.rgProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
props.rgProperties[0].vValue.vt = VT_BSTR;
props.rgProperties[0].vValue.bstrVal = SysAllocString(L"server_name");
props.rgProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;
props.rgProperties[1].vValue.vt = VT_BSTR;
props.rgProperties[1].vValue.bstrVal = SysAllocString(L"database_name");
IDBProperties* pIDBProperties = NULL;
hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void**)&pIDBProperties);
if (SUCCEEDED(hr)) {
hr = pIDBProperties->SetProperties(1, &props);
pIDBProperties->Release();
}
// Initialize the connection
hr = pIDBInitialize->Initialize();
if (FAILED(hr)) {
// Handle initialization failure
pIDBInitialize->Release();
return;
}
// Proceed with data access...
pIDBInitialize->Release();
HRESULT hr;
IDBInitialize* pIDBInitialize = NULL;
// Instantiate the data source object
hr = CoCreateInstance(CLSID_MSOLEDBSQL, NULL, CLSCTX_INPROC_SERVER,
IID_IDBInitialize, (void**)&pIDBInitialize);
if (FAILED(hr)) {
// Handle instantiation failure
return;
}
// Set properties (e.g., server, database)
DBPROPSET props = {0};
props.guidPropertySet = DBPROPSET_DBINIT;
props.cProperties = 2;
props.rgProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
props.rgProperties[0].vValue.vt = VT_BSTR;
props.rgProperties[0].vValue.bstrVal = SysAllocString(L"server_name");
props.rgProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;
props.rgProperties[1].vValue.vt = VT_BSTR;
props.rgProperties[1].vValue.bstrVal = SysAllocString(L"database_name");
IDBProperties* pIDBProperties = NULL;
hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void**)&pIDBProperties);
if (SUCCEEDED(hr)) {
hr = pIDBProperties->SetProperties(1, &props);
pIDBProperties->Release();
}
// Initialize the connection
hr = pIDBInitialize->Initialize();
if (FAILED(hr)) {
// Handle initialization failure
pIDBInitialize->Release();
return;
}
// Proceed with data access...
pIDBInitialize->Release();
Key Interfaces
The key interfaces in OLE DB form the foundation for data access, transaction management, and advanced operations, enabling consumers to interact with providers through standardized COM-based APIs. Mandatory interfaces ensure basic connectivity and data retrieval, while optional ones extend functionality for transactions, queries, metadata, and resource binding. These interfaces are implemented on specific OLE DB objects such as data source objects, sessions, and rowsets, allowing for modular and extensible data access. Among the mandatory interfaces, IDBInitialize is required on data source objects to manage the lifecycle of connections by initializing and uninitializing resources, such as establishing a connection to a data store upon calling itsInitialize method and releasing resources via Uninitialize.[22] Similarly, IDBCreateSession, also mandatory on initialized data source objects, enables the creation of session objects for scoped database operations through its CreateSession method, which returns an interface pointer to the new session for further interactions like executing commands or opening rowsets.[23] For direct access to tabular data, IOpenRowset is a required interface on sessions in providers that support table-based rowsets without commands; its OpenRowset method opens a rowset containing all rows from a specified base table or index, facilitating simple data retrieval without complex queries.[24] Complementing this, IRowset serves as the core interface on rowset objects for navigating and manipulating fetched data, offering methods like GetNextRows for sequential fetching, GetData for retrieving column values via accessors, ReleaseRows for resource cleanup, and RestartPosition to reset the cursor, thus enabling efficient forward-only or bookmark-based navigation through result sets.[25]
Transaction interfaces support ACID-compliant operations by allowing local and distributed transaction control. ITransactionJoin, an optional interface on sessions, enables enlisting in distributed transactions coordinated by an external transaction manager, with its JoinTransaction method joining a session to a specified transaction object and GetOptionsObject configuring join behaviors like isolation levels.[26] For local transactions, ITransactionLocal, another optional session interface inheriting from ITransaction, provides explicit control over transaction boundaries through StartTransaction to begin a new transaction, along with inherited Commit and Abort methods to ensure atomicity, consistency, isolation, and durability in single-resource operations.[27]
Advanced interfaces extend core functionality for sophisticated data handling. ICommand, mandatory on command objects created via sessions, supports executing text-based commands such as SQL statements, with methods like Execute to run the command and return rowsets or other objects, Cancel to interrupt execution, and GetDBSession to retrieve the originating session; it facilitates parameterized queries by allowing repeated executions with varying input values bound through accessors.[28] For metadata access, IDBSchemaRowset, an optional interface on data source or session objects, retrieves schema information via rowsets, using GetRowset to obtain details like tables (DBSCHEMA_TABLES), columns (DBSCHEMA_COLUMNS), or provider types (DBSCHEMA_PROVIDER_TYPES) with restriction columns to filter results, and GetSchemas to enumerate available schema GUIDs.[29] Additionally, IBindResource, mandatory on binder objects and optional on sessions or rowsets, supports binding to URL-identified resources for streaming data, with its Bind method returning a stream, rowset, or other object directly from a resource locator, enabling efficient access to large or remote data without full initialization.[30]
Security features are integrated through initialization interfaces and properties. IDataInitialize, a service-provided interface not tied to specific objects, simplifies secure connection establishment by creating data source objects from connection strings via GetDataSource, which can include authentication details like user IDs and passwords, or retrieving strings with GetInitializationString for persistence; it supports asynchronous initialization and interacts with properties such as DBPROP_AUTH_INTEGRATED (for Windows authentication) and DBPROP_AUTH_PASSWORD (for explicit credentials) to enforce secure access controls during connection setup.[31]
