Comparison of Aggregate and Block Storage

In This Section:

Introduction

Essbase provides an aggregate storage kernel as a persistence mechanism for multidimensional databases. Aggregate storage databases enable dramatic improvements in both database aggregation time and dimensional scalability. The aggregate storage kernel is an alternative to the block storage kernel. Aggregate storage databases typically address read-only, “rack and stack” applications that have large dimensionality, such as the following applications:

Customer analysis. Data is analyzed from any dimension, and there are potentially millions of customers.
Procurement analysis. Many products are tracked across many vendors.
Logistics analysis. Near real-time updates of product shipments are provided.

A sample application (ASOsamp), a data file, and a rules file are provided to demonstrate aggregate storage functionality.

Aggregate storage applications, which differ from block storage applications in concept and design, have limitations that do not apply to block storage applications. The following sections describe the differences.

Inherent Differences

Table 191. Inherent Differences Between Aggregate Storage and Block Storage

Inherent Differences	Aggregate Storage	Block Storage
Storage kernel	Architecture that supports rapid aggregation, optimized to support high dimensionality and sparse data	Multiple blocks defined by dense and sparse dimensions and their members, optimized for financial applications
Physical storage definition	Through the Application Properties window, Tablespaces tab in Administration Services	Through the Database Properties window, Storage tab in Administration Services
Create database	Migrate a block storage outline or define after application creation Note: Do not use the file system to copy a block storage outline into an aggregate storage application. Use the migration wizard in Administration Services to migrate the outline.	Define after application creation
Copy database	Not supported	Supported
Databases supported per application	One	Several (one recommended)
Application and database names	See Naming Restrictions for Applications and Databases. Names reserved for tablespaces, cannot be used as application or database names: default log metadata temp	See Naming Restrictions for Applications and Databases.
Application and database information display	Displayed in the Application Properties window and the Database Properties window in Administration Services. Information not supported by or relevant to aggregate storage applications is not shown. For a description of aggregate storage-specific information, see the Oracle Essbase Administration Services Online Help for the Application Properties window and Database Properties window.	Displayed in the Application Properties window and the Database Properties window in Administration Services
Configuration settings (essbase.cfg)	For a list of the settings that apply to aggregate storage databases, see the Oracle Essbase Technical Reference.	For a list of the settings that do not apply to block storage databases, see the Oracle Essbase Technical Reference.

Outline Differences

Table 192. Outline Differences Between Aggregate Storage and Block Storage

Outline Functionality	Aggregate Storage	Block Storage
Dense or sparse dimension designation	Not relevant	Relevant
Multiple hierarchies enabled, dynamic hierarchy, or stored hierarchy designation	Relevant	Irrelevant
Accounts dimensions and members on dynamic hierarchies	Support with the following exceptions: No two-pass calculation (however, for information on specifying the calculation order, see Calculation Order) No association of attribute dimensions with the dimension tagged Accounts Additional restrictions for shared members. See Alternate Hierarchies.	Full support
Members on stored hierarchies	Support with the following exceptions: Support for the ~ (no consolidation) operator (underneath label-only members only) and the + (addition) operator Cannot have formulas Restrictions on label only members (See Member storage types.) No Dynamic Time Series members Stored hierarchy dimensions cannot have shared members. Stored hierarchies within a multiple hierarchies dimension can have shared members. See Stored Hierarchies.	Full support
Member storage types	Support with the following exceptions: Dynamic Calc and Store not relevant On stored hierarchies, two limitations if a member is label only: All dimension members at the same level as the member must be label only The parents of the member must be label only. Note: On dynamic hierarchies, ability to tag any member as label only Note: On conversion from a block storage database, attribute dimension members are tagged as Dynamic Calc. On standard dimension members Dynamic Calc tags are converted and tagged as stored members, which changes the Members Stored value on the Dimensions tab of the Database Properties window in Administration Services.	Support for all member storage types in all types of dimensions except attribute dimensions
Ragged hierarchies and hierarchies with more than 10 levels	Support, with possible performance impact	Support
Outline validation	When database is started When outline is saved When block storage outline is converted to aggregate storage outline When user requests	When outline is saved When user requests
Outline paging	Support	No support
Database restructure	Levels of restructure; see Aggregate Storage Database Restructuring	Levels of restructure; see Optimizing Database Restructuring

Calculation Differences

Table 193. Calculation Differences Between Aggregate Storage and Block Storage

Calculation Functionality	Aggregate Storage	Block Storage
Database calculation	Aggregation of the database, which can be predefined by defining aggregate views	Calculation script or outline consolidation
Formulas	Allowed with the following restrictions: Must be valid numeric value expressions written in MDX; cannot contain the % operator—replace with expression: (value1 / value2) * 100 No support for Essbase calculation functions On dynamic hierarchy members, formulas are allowed without further restrictions	Support for Essbase calculation functions
Calculation scripts	Not supported	Supported
Attribute calculations dimension	Support for Sum	Support for Sum, Count, Min, Max, and Average
Calculation order	Member formula calculation order can be defined by the user using the solve order member property	Defined by the user in the outline consolidation order or in a calculation script

Partitioning Differences

Table 194. Partitioning Differences Between Aggregate Storage and Block Storage

Partitioning Functionality	Aggregate Storage	Block Storage
Partitioning	Support with the following restrictions: No outline synchronization	Fully supported

Data Load Differences

Table 195. Data Load Differences Between Aggregate Storage and Block Storage

Data Load Functionality	Aggregate Storage	Block Storage
Cells loaded through data loads	Only level 0 cells whose values do not depend on formulas in the outline are loaded	Cells at all levels can be loaded (except Dynamic Calc members)
Update of database values	At the end of a data load, if an aggregation exists, the values in the aggregation are recalculated	No automatic update of values. To update data values, you must execute all necessary calculation scripts.
Data load buffers	The loading of multiple data sources into aggregate storage databases is managed through temporary data load buffers	Not supported
Atomic replacement of the contents of a database	When loading data into an aggregate storage database, you can replace the contents of the database or the contents of all incremental data slices in the database	Not supported
Data slices	Aggregate storage databases can contain multiple slices of data. Data slices can be merged	Not supported
Dimension build for shared members	Full support for parent-child build method. Duplicate generation (DUPGEN) build method limited to building alternate hierarchies up to generation 2 (DUPGEN2).	Support for all build methods
Loading data mapped to dates	In a date-time dimension, you can load data into level 0 members using supported date-format strings instead of member names	Date-time dimension type is not supported

Query Differences

Table 196. Query Differences Between Aggregate Storage and Block Storage

Query Functionality	Aggregate Storage	Block Storage
Report Writer	Supported, except for commands related to sparsity and density of data	Fully supported
Smart View	Supported, with limited ability to change data (write-back)	Fully supported
API	Supported	Supported
Export	Support with the following restrictions: Export of level 0 data only (no upper-level export) No columnar export	Supported
MDX queries	Supported	Supported
Queries on attribute members that are associated with non-level 0 members	Returns values for descendants of the non-level 0 member. See also Design Considerations for Attribute Queries.	Returns #MISSING for descendants of the non-level 0 member
Queries on attribute members and shared members	A shared member automatically shares the attribute associations of its nonshared member	A shared member does not share the attribute associations of its nonshared member
Query logging	Not supported	Supported
Query performance	Considerations when querying data from a dimension that has multiple hierarchies. See Query Design Considerations for Aggregate Storage.	Hierarchies not relevant

Feature Differences

Table 197. Feature Differences Between Aggregate and Block Storage

Features	Aggregate Storage	Block Storage
Aliases	Supported	Supported
Currency conversion	Not supported	Supported
Hybrid analysis	Support with the following restriction: queries that contain a relational member and an Essbase member with a formula in the same query are not supported. For example, if California is a relational member, and the member Profit has a formula, the following report script returns an error: Jan California Profit !	Supported
Incremental data load	Supported	Supported
LROs	Not supported	Supported
Time balance reporting	Support with the following restrictions: Skip Zeros is not supported Time dimension must contain only stored hierarchies Shared members must be at level zero	Supported
Triggers	After-update triggers supported	On-update triggers and after-update triggers supported
Unicode	Supported	Supported
Variance reporting	Not supported	Supported
Date-time dimension type and linked attribute dimensions	Supported	Not supported
User ability to change data (write-back)	Transparent partition technique used to enable limited write-back	Fully supported