Various Caches Available in MicroStrategy/Bala Krishna Nutakki

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 browsedattributes are stored in the memory on the Intelligent Server and the MicroStrategyDesktop machine for faster retrievals.2. Object Caches : Definition of the frequentlyviewed metadata objects are stored on the I-Server and the MicroStrategyDesktop machines for faster retrieval.3. Report Caches : Results of previously executedreports are stored in the memory or disks on the I-Server machine, so that theycan be retrieved quickly, rather than re-executing the request against the warehouse database.4. Document Caches : Results of the report servicesDocument are stored in the memory or disk on the I-Server machine for faster retrieval.

 

Where do Caches Reside :

The table summarizes them

Caches Types and Location

CacheType

ClientMemory

ServerMemory

ServerDisk

Element Yes Yes

Object Yes Yes

Report Yes Yes

Document Yes Yes

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 eachProject on the I-Server machine and Object and Element Caches exists on theClient Machines too.

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

Element Caches :

An ElementCaches 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 theCustomer Attribute in the data Explorer in order to display a list of Customers.·If no element caches exist n the MS-Desktop or the Isever memory, the element request is send to the ware house for processing.·The list of Customers retrieved from the warehouse isthen stored as an Element Cache in the memory of the I-Server machine, and the MS-Desktop machine of the user whosubmitted the request.·If the same user requests the same attribute elements, the element cacheon 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.

ObjectCaches :

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 userobjects 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 ISerer machine, the object request is sent to the metadata for processing.·The report object definition is retrieved frommetadata and displayed to the user in the report editor.·An object cache is created in the memory of the I-Serverand MS-Desktop machines.·If the same user requests the same object, the objectcache on the local MS-Desktop machine satisfies the request.·If a different user requests the same report theobject cache in the I-Server memory satisfies that request.

Report Caches:

The I-Server provides report caching functionality thatreduce 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 runsa report.§ The reportruns against the data warehouse.§ The I-Servercaches the result set and returns the result to the user.§ A seconduser subsequently runs the same report.§ The I-Serversearches the report Caches.§ The I-Serverchecks the following variables.v Are thereport and any objects it contain unchanged since the cache is created.v For theprompted reports did the second user choose the same prompt answers as thefirst user.v Based on

the cache property and security settings, is the second user allowed to accessthe first user’s cache.v Is thecache still active ie. Is it not expired·If the answer to any of the variables is no, the cacheis not valid, and the I-Server queries the data warehouse. If the answer to allthe variables is Yes the cache is valid and the I-Server retrieves the resultset from cache.

Document Caching :

Report service document can be cached to improve the systemperformance and maintain a low memory footprint of the I-Server.

Document caches are created on the runtime or on schedule andbehave in a similar to the report caches. At runtime the document caches arecreated 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 XMLcache is generated with the data reflecting the new prompt answers.

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

1. Project Level2. Document Level.

microstrategy user

 

November 20, 2010