Types of Caches in Microstrategy

Different type of Caches Available in Microstrategy

What is Caching:

Caching is the retention of a recently used elements, objects, or report results for the purpose of improving the query response time in the further requests. Caching enables user to retrieve results from stored files rather that executing queries against a database.

There are four types of caches in Microstrategy

1. Element Caches:  Elements of frequently browsed attributes are stored in the memory on the intelligent server and MSTR desktop machines.
2. Object Caches: Definition of frequently used metadata objects are stored in the memory on the intelligent server and MSTR desktop machines
3. Report Caches: Results of previously executed reports are stored in the memory or disks on the I-server machine.
4. Document Caches:  Results of the report services Documents are stored in the memory or disks on the I-server machine.

In Two Tier mode: Object and Element caches exist on the Client Machine for

each Project that the Client accesses.

 In three tier mode: Object, Element, Report and Document caches exists for each Project on the I-Server machine and Object and Element Caches exists on the Client Machines too.

 Note :  Caches are Created and stored at the Project Level, Therefore they are not shared across Projects.

 Element Caches:  An Element Caches is a recently used attribute element list stored in the memory of MicroStrategy Desktop and I-Server machines.

 The example below illustrated is how element caches work.

• A MicroStrategy Desktop User double-Clicks the Customer Attribute in the data Explorer in order to display a list of Customers.
• If no element caches exist n the MS-Desktop or the I sever memory, the element request is send to the ware house for processing.
• The list of Customers retrieved from the warehouse is then stored as an Element Cache in the memory of the  I-Server machine, and the MS-Desktop machine of the user who submitted the request.
• If the same user requests the same  attribute elements, the element cache on the local MS-Desktop machine is used to satisfy that request.
•  If a different user requests the attribute elements, the Element Cache on the I-Server Memory is used to satisfy that request.

Note:  When a user requests elements, Element cache ID’s are matched to the element requests in order to determine if a cache can be used to satisfy the request.

Object Caches:

Object Caches is a recently used objects definition stored in the memory of the MS-Desktop and I-Server. We can create object caches for both application and schema objects.

The example below illustrates how object caches work:

• A user opens the report editor.
• The collection of attributes, metrics and other user objects are displayed in the report editor that makeup the report definition.
•  If no object cache for the report exists in the memory of the MS-Desktop or I Serer machine, the object request is sent to the metadata for processing.
• The report object definition is retrieved from metadata and displayed to the user in the report editor.
•  An object cache is created in the memory of the I-Server and MS-Desktop machines.
•  If the same user requests the same object, the object cache on the local MS-Desktop machine satisfies the request.
• If a different user requests the same report the object cache in the I-Server memory satisfies that request.

 Report Caches:

The I-Server provides report caching functionality that reduce the number of user requests that query the data warehouse. When an user initially runs the report the I-Server caches the result set. Subsequently, when a different user runs the same report again the I-Server can retrieve the result set from the cache rather than having to query the data warehouse again.

The example below illustrates how report caches work.

• A user runs a report.
• The report runs against the data warehouse.
• The I-Server caches the result set and returns the result to the user.
• A second user subsequently runs the same report.
• The I-Server searches the report Caches.
• The I-Server checks the following variables.

1. Are the report and any objects it contain unchanged since the cache is created.

2. For the prompted reports did the second user choose the same prompt answers as the first user.

3. Based on the cache property and security settings, is the second user allowed to access the first user’s cache.

4. Is the cache still active i.e. Is it not expired

 If the answer to any of the variables is no, the cache is not valid, and the I-Server queries the datawarehouse. If the answer to all the variables is Yes the cache is valid and the I-Server retrieves the result set from cache

Document Caching:

Report service document can be cached to improve the system performance and maintain a low memory footprint of the I-Server. Document caches are created on the runtime or on schedule and behave in a similar to the report caches. At runtime the document caches are created only in MS-Web.

For example when you execute a prompted document in MS-Web, an XML document cache is generated. When you reprompt the document, a new XML cache is generated with the data reflecting the new prompt answers.

 You can configure the Document Caching properties at two different levels.

1.     Project Level

2.     Document Level.