Tài liệu Module 8: Managing Storage and Optimization pptx

Contents Overview 1 Analysis Server Cube Storage 2 The Storage Design Wizard 10 Analysis Server Aggregations 17 Lab A: Designing Storage for Sales 23 Usage-Based Optimization 28 Lab B: Implementing Usage-Based Optimization 35 Optimization Tuning 39 Review 41 Module 8: Managing Storage and Optimization BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Information in this document is subject to change without notice. The names of companies, products, people, characters, and/or data mentioned herein are fictitious and are in no way intended to represent any real individual, company, product, or event, unless otherwise noted. Complying with all applicable copyright laws is the responsibility of the user. No part of this document may be reproduced or transmitted in any form or by any means, electronic or mechanical, for any purpose, without the express written permission of Microsoft Corporation. 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Microsoft is listed first, followed by all other Microsoft trademarks in alphabetical order. > are either registered trademarks or trademarks of Microsoft Corporation in the U.S.A. and/or other countries. <This is where mention of specific, contractually obligated to, third party trademarks, which are added by the Copy Editor> The names of companies, products, people, characters, and/or data mentioned herein are fictitious and are in no way intended to represent any real individual, company, product, or event, unless otherwise noted. Other product and company names mentioned herein may be the trademarks of their respective owners. Module 8: Managing Storage and Optimization iii BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Instructor Notes This module provides students with a comprehensive understanding of Microsoft ® SQL Server ™ Analysis Services storage options and optimization techniques for online analytical processing (OLAP) cubes. The characteristics of the three storage modes—multidimensional OLAP (MOLAP), relational OLAP (ROLAP), and hybrid OLAP (HOLAP)—are reviewed in detail followed by an overview of aggregations. The module then takes students through the Storage Design Wizard with discussion of specific aggregation options and further discussion of the contents of aggregations and design guidelines. The module concludes with a review of usage-based optimization and general optimization tuning techniques. There are two labs in the module. In lab A, students create a storage design and process a cube by using the Storage Design Wizard. In lab B, students learn the interfaces and mechanics of usage-based optimization. After completing this module, students will be able to: ! Explain the advantages and disadvantages of the three data storage modes. ! Use the Storage Design Wizard to set storage design. ! Describe how aggregations work and design aggregations for cubes. ! Describe the concepts and mechanics of usage-based optimization. ! Override aggregation settings per dimension. Materials and Preparation This section lists the required materials and preparation tasks that you need to teach this module. Required Materials To teach this module, you need the following materials: ! Microsoft PowerPoint ® file 2074A_08.ppt Preparation Tasks To prepare for this module, you should: ! Read all the student materials. ! Read all the instructor notes and margin notes. ! Practice the lecture presentation and demonstration. ! Complete the labs. ! Review the Trainer Preparation presentation for this module on the Trainer Materials compact disc. ! Review any relevant white papers that are located on the Trainer Materials compact disc. Presentation: 70 Minutes Labs: 20 Minutes iv Module 8: Managing Storage and Optimization BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Demonstration: Designing Storage for the Sales Cube In this demonstration, you will learn how to create a storage design by using the Storage Design Wizard. The following demonstration procedures contain information that does not fit in the margin notes or is not appropriate for student notes. ! To restore a new database and define a data source 1. In Analysis Manager, right-click the server, click Restore Database, click the Look in list, find and click the file C:\Moc\2074A\Labfiles\L08\Module 08.CAB, click Open, and then click Restore. 2. Click Close, and then double-click Module 08 to expand the database. 3. Below Module 08, double-click Data Sources, right-click the Module 08 data source, and then click Edit. 4. Click the Connection tab of the Data Link Properties dialog box, and then verify that localhost is selected in step 1. 5. In step 2, verify that Use Windows NT Integrated security is selected. 6. In step 3, verify that Module 08 is selected. 7. Click Test Connection and verify that the test succeeded. Click OK twice. ! To specify storage type 1. In the Module 08 database, right-click the Sales cube and click Design Storage. 2. Click Next to skip the welcome page. 3. From the Select the type of data storage step, click MOLAP, and then click Next. ! To design aggregations 1. In the Set aggregation options step, click Performance gain reaches from the Aggregation options pane. 2. Type 20 in the percent box for Performance gain reaches to reflect a 20- percent aggregation target. For the Sales cube, the default value of 50 is unnecessarily high. 3. Click Start to initiate the graphical simulation of Performance vs. Size on the Set aggregation options step, and then click Next. Demonstration: 10 Minutes Module 8: Managing Storage and Optimization v BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY ! To process the cube 1. In the Finish the Storage Design Wizard step and with the Process now option clicked, click Finish. Regardless of the processing option you choose, Analysis Manager stores the definition of the aggregations in the OLAP repository. Storing the definition of the aggregations is different from physically creating them, however. The Storage Design Wizard designs aggregations but does not create them. The Analysis Server does not create aggregations until you process the cube. Processing the cube automatically creates any aggregations that have been designed. 2. Close the Process dialog box when processing is complete. ! To examine the metadata 1. In Analysis Manager, click the Sales cube in the Analysis Manager tree pane and then click Metadata in the right details pane. 2. Scroll down and notice the process and storage mode statistics. vi Module 8: Managing Storage and Optimization BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Other Activities Difficult Questions Below are difficult questions that students may ask you during the delivery of this module and answers to the questions. These materials delve into subjects that are within the scope of the module but are not specifically addressed in the content of the student notes. 1. If ROLAP is slow to process and query, why would an organization use this option? ROLAP would be adopted if the organization needs a real-time OLAP solution—that is, data is always updated with the current fact table values. In this scenario, an organization defines its cube as ROLAP with zero aggregations. All detail and aggregate data are calculated as users query the cube. While queries are slow, in some situations perfectly updated data is more important than fast query times. 2. Do Analysis Services MOLAP cubes have the “data explosion” problem common to OLAP solutions? MOLAP database engines in competing products often create cubes that grow exponentially from source files to fully calculated cubes. For example, a five-megabyte (MB) source file has been known to grow into a five-gigabyte (GB) cube after processing. The data explosion problem when using MOLAP in Analysis Services does not exist to the extent experienced with other OLAP products. In many cases, the MOLAP cube may be smaller than the data source. The following are the principal reasons for the MOLAP storage efficiency: • Analysis Services MOLAP cubes are completely dense in their data storage—that is, no null values are stored. • The Analysis Services query engine is highly optimized, calculating commonly accessed aggregations as the cube is queried so that fewer aggregations need to be precalculated and stored. • The Analysis Services data compression algorithms are highly efficient. Some multidimensional products presumably solve the data explosion problem by not using an OLAP engine, instead accessing data directly from a relational database. Such products classify themselves as ROLAP solutions because they access relational databases directly and give users a multidimensional view of the data, but do not create cubes that consume large amounts of storage. Such ROLAP solutions typically suffer in query performance compared to MOLAP solutions. Module 8: Managing Storage and Optimization vii BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 3. MOLAP cubes duplicate the detail data already stored in relational tables. How can MOLAP storage be more efficient than ROLAP cube storage? How can MOLAP be faster to process than ROLAP if Analysis Services brings all the detail data to the Analysis Server? Multidimensional structures and data are extremely compressed and optimized compared to the two-dimensional tables in relational databases. In addition, when defining ROLAP cubes, indexes are automatically created in the relational database management system (RDBMS). Even though MOLAP cubes carry over the detail data, they can still be smaller than their ROLAP cube counterparts. The exception is a ROLAP cube that has few or no aggregations. From a processing standpoint, it may be faster to create a multidimensional structure than to create, insert, and update data in relational tables. It also may take a long time to build the indexes that are automatically created in ROLAP cubes. Again, the exception is when the ROLAP cube has few or no aggregations defined. 4. If processing time and disk space are not constraints, should aggregations be set to 100 percent for Performance gains reaches? If Performance gains reaches is set to 100 percent, all a cube’s possible aggregations will not necessarily be computed. The setting simply targets that query performance will be potentially increased by 100 percent. As a cube defines more aggregations, query performance improvements reach a point of diminishing returns. Some cubes may slow in their query performance if the aggregation percentage is set too high. 5. How does one estimate the size of a cube based on fact table size? You can estimate the data storage for MOLAP data on disk in bytes, assuming zero aggregations, by using the following formula: (((2 * total number of levels) + (4 * number of measures)) * number of records) / 3 6. Analysis Services has intelligent algorithms for determining the most optimized aggregation design. Why would you choose to override the dimension level aggregations? In most cases, you use the Storage Design Wizard and the Usage-Based Optimization Wizard to define aggregations. However, there may be exceptional situations in which you might want to exercise control, overriding wizard algorithms. For example, you might not want your cube to contain aggregations for the lowest level of the Product dimension, because users will not be accessing data at that level. Therefore, you have the ability to turn off aggregations for this level. viii Module 8: Managing Storage and Optimization BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module Strategy Use the following strategy to present this module: ! Analysis Server Cube Storage Deliver an overview discussion of general server storage issues and then talk through the characteristics of each of the three storage modes— MOLAP, ROLAP, and HOLAP. This discussion leads into a basic introduction to the concept of aggregations. ! The Storage Design Wizard The materials in this section can be delivered as lecture by using the slides or integrated with the demonstration Design Storage for the Sales Cube. Because the demonstration essentially duplicates the materials in the student notes, it is recommended to integrate lecture and demonstration. The following table is a mapping of lecture topics to demonstration steps. Lecture Topic Demonstration Procedure Choose Storage Option To specify storage type Set Aggregation Options To design aggregations How Much Aggregation? To design aggregations Estimated Storage Reaches To design aggregations Performance Gain Reaches To design aggregations Until I Click Stop To design aggregations Finishing Up To examine the metadata and browse the cube There will be substantial interest and questions from students about the storage size and performance implications of choosing from each of the three storage methods. Do not rush through these materials or limit discussion and questions. Review the questions and answers in the previous Difficult Questions section. Be prepared to discuss elements of aggregation again, including the specific functioning of the three aggregation options—Estimated storage reaches, Performance gain reaches, and Until I click stop. These three choices represent different conceptual approaches and specific underlying algorithms for implementing aggregations. ! Analysis Server Aggregations The subject of aggregation is explored in more detail, including review of aggregation tables, general characteristics of aggregations, and details about ROLAP aggregations. Because students must thoroughly understand the concepts and wizard implementation of aggregations, the subject is approached repeatedly in this module at increasing levels of detail and sophistication. Lab A follows the aggregation details section. Students now have an opportunity to create storage designs of their own based on MOLAP and ROLAP storage modes. The lab essentially replicates the steps performed in the demonstration. Module 8: Managing Storage and Optimization ix BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY ! Usage-Based Optimization This section presents an important feature set of Analysis Services—usage- based optimization. Your lecture, following the materials in the student notes, takes students through the simple Usage-Based Optimization Wizard. Be prepared to answer detailed questions about how each of the five query options work by themselves and in conjunction with each other. The section is followed by lab B, Implementing Usage-Based Optimization, which can be conducted as a hands-on exercise with students following your demonstration. The lab allows students to perform their own usage-based optimizations. ! Optimization Tuning You complete the module with a discussion of specific optimization tuning methods, including how to override dimension and level settings. No exercises or labs are included in this section. However, you should switch to Analysis Manager to show the settings and to briefly explain their functions. [...].. .Module 8: Managing Storage and Optimization 1 Overview Topic Objective To provide an overview of the module topics and objectives ! Analysis Server Cube Storage Lead-in ! The Storage Design Wizard ! Analysis Server Aggregations ! Usage-Based Optimization ! Optimization Tuning In this module, you will learn about aggregation design and storage modes, which are the key... the right details pane 2 Scroll down and notice the process and storage mode statistics BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 26 Module 8: Managing Storage and Optimization Exercise 2 Modifying the Storage of the Sales Cube In this exercise, you will update the storage design for the Sales cube You will apply the ROLAP storage mode and redesign aggregations In addition,... partition in a cube, and then click Design Storage The user interface of the Storage Design Wizard differs depending on: ! Whether storage has been designed previously for the cube ! Whether the cube contains partitions BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 8: Managing Storage and Optimization 11 Choosing a Storage Mode Topic Objective To review storage options... sizes and processing times Tools for Implementing Aggregations In the following sections, you will learn about three tools available to you for implementing aggregations: ! Storage Design Wizard ! Usage-Based Optimization Wizard ! Dimension and Level aggregation properties BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 10 Module 8: Managing Storage and Optimization # The Storage. .. Describe how aggregations work and design aggregations for cubes ! Describe the concepts and mechanics of usage-based optimization ! Override aggregation settings per dimension BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 2 Module 8: Managing Storage and Optimization ` # Analysis Server Cube Storage Topic Objective To introduce Analysis Services storage options Lead-in Analysis... the storage type At the first step of the wizard, you must specify the storage type: MOLAP, ROLAP, or HOLAP The selected storage mode determines query performance, processing performance, and cube storage Therefore, you must determine the appropriate storage mode before starting the Storage Design Wizard BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 12 Module 8: Managing Storage. .. learn how to create a storage design by using the Storage Design Wizard The steps for this demonstration are included in the Instructor Notes BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 8: Managing Storage and Optimization 23 Lab A: Designing Storage for Sales Topic Objective To introduce the lab Lead-in In this lab, you will design storage and aggregations for the... have both a MOLAP partition and a ROLAP partition Note For more information about partitions, see module 10, Managing Partitions,” in course 2074A, Designing and Implementing OLAP Solutions with Microsoft SQL Server 2000 BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 8: Managing Storage and Optimization ! 3 Analysis Server does not allocate storage for missing values... PREPARATION PURPOSES ONLY 16 Module 8: Managing Storage and Optimization Finishing Up Topic Objective To show the options offered at the last step of the Storage Design Wizard Lead-in At the last step of the Storage Design Wizard, you have four options You have four options at the last step of the Storage Design Wizard: ! Process now Writes the aggregation metadata to the repository, and then processes the... 22 Module 8: Managing Storage and Optimization Demonstration: Designing Storage for the Sales Cube Topic Objective To demonstrate the design of a cube’s storage mode so that students become familiar with the interface Lead-in Let us see an example of storage design by using the Sales cube Delivery Tips Deliver this demonstration integrating the previous lecture materials, which cover details of the Storage . Storage Design Wizard ! Usage-Based Optimization Wizard ! Dimension and Level aggregation properties Note 10 Module 8: Managing Storage and Optimization. pane and then click Metadata in the right details pane. 2. Scroll down and notice the process and storage mode statistics. vi Module 8: Managing Storage