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Comparison of Aggregate and Block Storage


Essbase Analytic Services 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:

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

Differences Between Aggregate and Block Storage

Aggregate storage applications differ from block storage applications in both concept and design. Additionally, aggregate storage applications have some limitations that do not apply to block storage applications. The following tables describe the differences between aggregate and block storage.


Table 1: 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 Essbase Administration Services

Through the Database Properties window, Storage tab in Essbase Administration Services.

Database creation

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

Databases supported per application

One

Several

Application and database names

Names reserved for tablespaces, cannot be used as application or database names:

  • default

  • log

  • metadata

  • temp

No reserved names

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 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 Technical Reference.

For a list of the settings that do not apply to block storage databases, see the Technical Reference.




Table 2: Outline Differences Between Aggregate Storage and Block Storage  

Outline Functionality
Aggregate Storage
Block Storage

Dense or sparse dimension designation

Not relevant

Relevant

Accounts dimensions

Support with the following exceptions:

  • No time balance members

  • No two-pass calculation

  • No association of attribute dimensions (See also Formulas.)

Full support

Non-accounts dimensions

Support with the following exceptions:

  • No member formulas

  • Support for only the + (addition) consolidation operator

  • Restrictions on label only members

  • No Dynamic Time Series members

(See also Member consolidation properties and Member storage types.)

Full support

Member consolidation properties

For non-accounts dimensions, support for only the + (addition) consolidation operator

For all dimensions, support for all consolidation properties

Member storage types

Support with the following exceptions:

  • No shared members

  • Never Share member not relevant

  • Dynamic Calc and Store not relevant

  • On non-accounts dimensions, 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 accounts dimensions, 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

The following actions cause Analytic Services to restructure the outline and clear all data:

  • Add, delete, or move a standard dimension member

  • Add, delete, or move a standard dimension

  • Add, delete, or move an attribute dimension

  • Add a formula to a level 0 member

  • Delete a formula from a level 0 member

The following actions cause an outline restructure, but do not clear the data:

  • Add, delete, or move an attribute dimension member

  • Add or delete a formula from a non-level 0 member

  • Rename a member or dimension

  • Add or delete an alias

  • Add or delete member comments or extended member comments

  • Add or delete a user-defined attribute (UDA)

  • Associate or disassociate an attribute dimension

Several levels of restructure. See Optimizing Database Restructuring.




Table 3: 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:

  • Only in the dimension tagged as accounts

  • Must be valid numeric value expressions written in MDX (cannot contain % operator, replace with expression: (value1/value2)*100)

  • No support for Analytic Services calculation functions

Allowed in all dimension types

Calculation scripts

Not supported

Supported

Attribute calculations dimension

Support for Sum

Support for Sum, Count, Min, Max, and Average

Calculation order

Not relevant (Predefined by the outline)

Defined by the user in the outline consolidation order or in a calculation script




Table 4: Partitioning and Write Back Differences Between Aggregate Storage and Block Storage

Partitioning and Write-Back Functionality
Aggregate Storage
Block Storage

Partitioning

Support with the following restrictions:

  • Transparent partitions only

  • Aggregate storage database as the source database

  • No outline synchronization

Support with no restrictions

User ability to change data (write back)

Transparent partition technique used to enable limited write back

Full support




Table 5: 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

Update of database values

At the end of a data load, if an aggregation exists, the values in the aggregation are recalculated and updated.

No automatic update of values. To update data values you must execute all necessary calculation scripts.

Incremental data load

Data values are cleared each time the outline is changed structurally. Therefore, incremental data loads are supported only for outlines that do not change (for example, logistics analysis applications).

Outline changes do not automatically clear data values, even if a data source is used to both modify members and load values. Therefore, incremental data loads are supported for all outlines.




Table 6: 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

Spreadsheet Add-in

Supported, with limited ability to change data (write back)

(See User ability to change data (write back).)

Fully supported

API

Supported

Supported

Export

Not supported, except for the MaxL export data using report_file grammar

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.

Returns #MISSING for descendants of the non-level 0 member.



Features Supported by Aggregate and Block Storage

Some features are not supported for aggregate storage. The following table describes the differences between aggregate and block storage.


Table 7: Features Supported by Aggregate and Block Storage  

Features
Aggregate Storage
Block Storage

Aliases

Supported

Supported

Currency conversion

Not supported

Supported

Data mining

Not supported

Supported

Hybrid analysis

Support with the following restriction: queries that contain a relational member and an Analytic Services 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

Linked reporting objects (LROs)

Not supported

Supported

Time balance reporting

Not supported

Supported

Triggers

After-update triggers supported

On-update triggers and after-update triggers supported

Unicode

Not supported

Supported

Variance reporting

Not supported

Supported





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