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Show / Hide Table of Contents
  • Programmer's Guide
  • Client Side API Programming
    • Setting Up Development Environment
    • Basic Cache Operations
      • Initialize Cache
      • Add Data to Cache
      • Update Data in Cache
      • Fetch Data From Cache
      • Remove Data From Cache
      • Dispose Cache
    • Bulk Operations
      • Adding Collection to Cache
      • Updating Collection in Cache
      • Retrieving Collection from Cache
      • Removing Collection from Cache
      • Deleting Collection from Cache
    • Asynchronous Operations
      • Using Asynchronous Operations
      • Using Asynchronous Operations with Callback Methods
    • Groups and Subgroups
      • Adding/Updating Data Group in Cache
      • Retrieving Data Group from Cache
      • Removing Data Group from Cache
    • Tagging Data in NCache
      • Creating Tags
      • Adding Items with Tags
      • Retrieving Previously Tagged Data
      • Removing Tagged Items from Cache
    • Named Tags
    • Data Expiration Strategies
      • Using Absolute Expiration
      • Using Sliding Expiration
    • Cache Dependencies
      • Key Dependency
      • File Dependency
      • Notification based Dependencies
        • Database Dependency using SQL Server
        • Database Dependency using Oracle
      • Polling Based Dependency
      • Custom Data Source Dependency
      • Multiple Cache Sync Dependency
      • Aggregate Dependency
      • Add Dependency to Existing Item
      • Using CLR Procedures to Call NCache
    • Locking Data in NCache
      • Locking Items in Cache (Pessimistic Locking)
      • Locking Items with Cache Item Versioning (Optimistic Locking)
    • SQL Reference for NCache
      • SQL Syntax
      • Querying Samples for Operators
      • Querying Data in NCache
      • NCache Language Integrated Query (LINQ)
        • Using LINQ in NCache
        • Configuring LINQPad for NCache
        • Querying NCache Data in LINQPad
    • Event Notifications
      • Cache Level Event Notifications
      • Item Level Event Notifications
      • Custom Event Notifications
    • Publish/Subscribe (Pub/Sub) in NCache
      • Pub/Sub Topics
      • Managing Topics
      • Pub/Sub Messages
        • Message Behavior and Properties
        • Creating a Message
      • Publish Messages to Topic
      • Subscribe for Topic Messages
      • Monitoring Pub/Sub Topics
    • Continuous Query
    • Using Streams in NCache
      • Opening with Stream Modes
      • Adding and Updating Data with Streams
      • Retrieving Data from Streams
      • Closing a Stream
    • Security and Encryption
      • NCache Security
      • NCache Data Encryption
    • Data Compression
    • NCache Management API
  • Server Side API Programming
    • Cache Startup Loader
      • Components of Cache Startup Loader
      • Sample Implementation of ICacheLoader on Single Node
      • Sample Implementation of ICacheLoader with Distribution Hints
    • Data Source Providers (Backing Source)
      • Read-Through Caching
        • Configure Read-Through Provider
        • Using Read-Through with Cache Operations
      • Write-Through Caching
        • Configuring Write-Through Provider
        • Using Write-Through with Basic Operations
        • Using Write-Behind with Basic Operations
        • Using Write-Behind with Bulk Operations
        • Using Write-Behind with Async Operations
        • Monitor Write-Through Counters
    • Custom Dependency
      • Sample Implementation of Custom Dependency
      • Sample Usage of Custom Dependency
    • WAN Replication through Bridge
      • Bridge Configurations
      • Implementing Bridge Conflict Resolver
    • Entry Processor
      • Sample Implementation of IEntryProcessor Interface
      • Sample Usage of EntryProcessor
    • MapReduce
      • Sample Implementation of MapReduce Interfaces
      • Sample Usage of MapReduce
    • Aggregator
      • Sample Implementation of IValueExtractor Interface
      • Sample Implementation of IAggregator Interface
      • Sample Usage of Aggregator
    • Dynamic Compact Serialization
  • Client Side ASP.NET Features
    • ASP.NET
      • ASP.NET Session State Provider for NCache
      • Multi-Region ASP.NET Session State Provider for NCache
    • ASP.NET Core
      • Session Storage in ASP.NET Core
        • Configure NCache ASP.NET Core Session Provider
        • Configure ASP.NET Core Sessions with NCache IDistributedCache Provider
      • Multi-Region ASP.NET Core Session Provider for NCache
      • Object Caching in ASP.NET Core
    • ASP.NET SignalR
      • Using NCache Extension for SignalR
    • View State Caching
      • Configuring and Using Content Optimization
      • Group View State with Sessions
      • Limit View State Caching
      • Perform Page Level Grouping for View State
    • ASP.NET Output Cache
      • Configure ASP.NET Output Caching
      • Using ASP.NET Output Cache with Custom Hooks
  • Client Side Third Party Integrations
    • Migrating AppFabric to NCache
      • AppFabric API vs. NCache API
    • NHibernate
      • NCache as NHibernate Second Level Cache
      • Using NHibernate Query Caching
      • Configuring Database Synchronization with NHibernate
    • Entity Framework Caching Integration
      • NCache as Entity Framework Second Level Cache
      • Entity Framework Caching Config File
    • Entity Framework Core Caching
      • Installing NCache Entity Framework Core Provider
      • Configuring NCache Entity Framework Core Provider
      • Using NCache Entity Framework Core Provider
        • Caching Options for EF Core Provider
        • LINQ APIs for EF Core Provider
        • Cache Only APIs for EF Core Provider
        • Query Deferred APIs for EF Core Provider
      • Logging in NCache Entity Framework Core Provider
    • Memcached
      • NCache Memcached Gateway Approach
      • Memcached Client Plugin for .NET
    • Debug NCache Providers in Visual Studio
    • NCache for Visual Studio Extension

Database Dependency Using Oracle

NCache provides OracleCacheDependency for notification based dependencies with Oracle. Internally, NCache uses OracleDependency to register data change notifications with the Oracle database server. Hence you need to understand the limitations and working mechanisms of OracleDependency while using this dependency. For example, limited sets of queries can be registered with OracleDependency. See Special Considerations Using Query Notifications and OracleDependency class for more detail.

Oracle Dependency is provided by NCache for synchronizing cache with Oracle database. Item expires if result of the command (based on command text) changes. Oracle Dependency is only available for Oracle database 10g release 2 or later. Also make sure that Oracle Data Providers for .NET (version 10.1.0.2.0 or later) is installed.

Configuring Notification on Oracle Server

NCache tracks changes in a database using notifications received from Oracle server about changes in the database. For this purpose, NCache registers CHANGE NOTIFICATION with the Oracle server. NCache server should have the CHANGE NOTIFICATION privileges to create a notification registration. If NCache server machine does not have these privileges, the following statement can be used to grant the CHANGE NOTIFICATION privilege to the user.

Adding Data with Oracle Dependency

The following code shows how to add data with OracleCacheDependency. Altering data after addition with Oracle Dependency will remove it from cache.

To utilize the API, include the following namespace in your application: Alachisoft.NCache.Runtime.Dependencies.

  //Create object to be added with dependency
  Product product = new Product();
  product.ProductID = 1001;
  product.ProductName = "Chai";
  string key = "Product:" + product.ProductID;
  try{   
       //Creating OracleCacheDependency
      string connectionString = "User Id=scott;Password=tiger;Data Source=oracle";
      string query = "SELECT rowID, productID FROM dbo.Products WHERE productID = 1001";

      OracleCacheDependency oracleDependency = new OracleCacheDependency(connectionString, query);

      //Adding cache item "Product:1001" with SqlDependency
      cache.Insert(key, product, oracleDependency, Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration, CacheItemPriority.Normal);

      //Modify Product record in database while program waits...
      Thread.Sleep(5000);

      //... and then check for its existence
      Object item = cache.Get(key);
      if (item == null){
            // item removed successfully
      }
      else{
            // item not removed successfully
      }
  }
  catch (OperationFailedException e){ }

In Oracle 10g, database change notifications are only object based. This means that change notifications will be fired if any row is modified in an object. Therefore, it is recommended to check rowID to confirm if the altered row is the one for which the event was registered. RowIDs cannot be retrieved unless explicitly included in query. So the user has to specifically include rowID in the query that is being registered with OracleDependency, otherwise the change notification will be fired if any row is modified in table.

When rowID is included in a query such as – Select rowID, productID, productname, unitprice from Products where ProductID = 220 - NCache will save the rowIDs of rows for which the change notification is registered. When it receives any change notification, NCache will compare the rowIDs to determine whether the row changed is the one for which the rowID is registered. Otherwise NCache will have no way to check against this and items for which change notification is registered may be removed if any row in the table changes.

In Oracle 11g, both object based and query based (default) notifications are provided. In query based notifications, change of the modified row will be notified only if the change notification is registered for it.

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