In the OLAP world, there are
mainly two different types: Multidimensional OLAP
(MOLAP) and Relational OLAP (ROLAP). Hybrid OLAP (HOLAP) refers to
technologies
that combine MOLAP and ROLAP.
MOLAP
This is the more
traditional way of OLAP analysis. In MOLAP, data is stored
in a multidimensional cube. The storage is not in the relational
database, but
in proprietary formats.
Advantages
:
- Excellent performance:
MOLAP cubes are built for fast data retrieval, and
is optimal for slicing and dicing operations.
- Can perform complex calculations: All calculations have been
pre-generated
when the cube is created. Hence, complex calculations are not only
doable, but
they return quickly.
Disadvantages
:
- Limited in the amount of
data it can handle: Because all calculations
are performed when the cube is built, it is not possible to include a
large
amount of data in the cube itself. This is not to say that the data in
the
cube cannot be derived from a large amount of data. Indeed, this is
possible. But in this case, only summary-level information will be
included
in the cube itself.
- Requires additional investment: Cube technology are often
proprietary and
do not already exist in the organization. Therefore, to adopt MOLAP
technology,
chances are additional investments in human and capital resources are
needed.
ROLAP
This methodology
relies on manipulating the data stored in the relational
database to give the appearance of traditional OLAP's slicing and dicing
functionality. In essence, each action of slicing and dicing is
equivalent to
adding a "WHERE" clause in the SQL statement.
Advantages
:
- Can handle large amounts of
data: The data size limitation of ROLAP technology
is the limitation on data size of the underlying relational database.
In other
words, ROLAP itself places no limitation on data amount.
- Can leverage functionalities inherent in the relational
database: Often,
relational database already comes with a host of functionalities. ROLAP
technologies, since they sit on top of the relational database, can
therefore
leverage these functionalities.
Disadvantages
:
- Performance can be slow:
Because each ROLAP report is essentially a SQL
query (or multiple SQL queries) in the relational database, the query
time
can be long if the underlying data size is large.
- Limited by SQL functionalities: Because ROLAP technology
mainly relies
on generating SQL statements to query the relational database, and SQL
statements do not fit all needs (for example, it is difficult to perform
complex calculations using SQL), ROLAP technologies are therefore
traditionally limited by what SQL can do. ROLAP vendors have mitigated
this risk by building into the tool out-of-the-box complex functions as
well
as the ability to allow users to define their own functions.
HOLAP
HOLAP
technologies attempt to combine the advantages of MOLAP and ROLAP. For
summary-type information, HOLAP leverages cube technology for faster
performance.
When detail information is needed, HOLAP can "drill through" from the
cube into
the underlying relational data.
分享到:
相关推荐
数据仓库建模,olap(rolap、molap、holap)建模分析;数据仓库建模,olap(rolap、molap、holap)建模分析;数据仓库建模,olap(rolap、molap、holap)建模分析;
数据仓库与OLAP技术浅显易懂的入门介绍,主要介绍了数据仓库与分析处理工具/OLAL/MOLAP/ROLAP/HOLAP几种。
MOLAP ROLAP HOLAP Essbase介绍 • Essbase作用 • Essbase特点 • Essbase应用场景 Hyperion Essbase简介 Essbase:分析过去、监控现在、预测未来 Essbase : 全方位的分析解决方案 Essbase:全面的财务分析 ...
其具体实现可以分为:ROLAP(关系型在线分析处理)、MOLAP( 多维在线分析处理)和HOLAP(混合型线上分析处理)。ROLAP基本数据和聚合数据均存 放在RDBMS之中;MOLAP基本数据和聚合数据均存放于多维数据库中
OLAP(联机分析处理)。 什么是联机分析处理(OLAP) 联机分析处理 (OLAP) 的概念最早是由关系数据库之父E.F.Codd于1993年提出的,他...OLAP有多种实现方法,根据存储数据的方式不同可以分为ROLAP、MOLAP、HOLAP。
9.2.1 选择存储模式:MOLAP、HOLAP和ROLAP 196 9.2.2 OLTP表的分区 198 9.2.3 其他OLAP分区配置 199 9.3 实现聚合 199 9.3.1 聚合设计向导 200 9.3.2 基于使用情况的优化向导 202 9.3.3 SQL Server Profiler 203 ...
9.2.1 选择存储模式:MOLAP、HOLAP和ROLAP 196 9.2.2 OLTP表的分区 198 9.2.3 其他OLAP分区配置 199 9.3 实现聚合 199 9.3.1 聚合设计向导 200 9.3.2 基于使用情况的优化向导 202 9.3.3 SQL Server Profiler 203 ...
9.2.1 选择存储模式:MOLAP、HOLAP和ROLAP 196 9.2.2 OLTP表的分区 198 9.2.3 其他OLAP分区配置 199 9.3 实现聚合 199 9.3.1 聚合设计向导 200 9.3.2 基于使用情况的优化向导 202 9.3.3 SQL Server Profiler 203 ...
9.2.1 选择存储模式:MOLAP、HOLAP和ROLAP 196 9.2.2 OLTP表的分区 198 9.2.3 其他OLAP分区配置 199 9.3 实现聚合 199 9.3.1 聚合设计向导 200 9.3.2 基于使用情况的优化向导 202 9.3.3 SQL Server Profiler ...