how to resolve the loop in universe level

[Former Member]

how to resolve the loop in universe level

[Former Member]

Hi

You can use alias table or context to resolve the loop.

Regards,

Amala.S

[Former Member]

Hi,

Loop is nothing but a closed path.this will happen when you join the tables like Table A-->Table B-->Table C-->table A.

In this situation you wont get the result you wanted. either you may get more or less expected result.

to resolve the loop you need to create either alias or context.

Create an alias table for Table C and join the table with A. Then the path will be open and you will get exact result.

[Former Member]

Hi, Kashim

          In univese level loops resolved by Chasm Trap and Fan Trap methods.

Chasm Trap:  A chasm trap is a type of join path between three tables when two many-to-one joins converge on single table, and there is no context in place that separate the converging join paths.

There is "many-to-one-to-many"relationship beween the three tables in the universe structure.you can define a context for each table at the many end of the joins.

A chasm trap is not dependent on the object types, the query could be made up of only dimensions,only details,or only measures,or any combination of the three types with the "many " tables for chasm to occure.

you can also detect the chasm trap Automatically, tool---->Detect context

To resolve the chasm trap, you need to make two separate Queries and than combine the results Depending on type of objects defined for the fact tables and the type of end user environment,

Fan trap: it is occured when there is a "one-to-many" join to the table that "fans out " into another "one-to-many" join to another table.

Avoid fan trap: The first place by relating all measure objects in the universe to the same table in the universe structure,Avoid placing a measure on anything other than the last table in a in a table path, which is the table with the "many" cardinality attached to it.

This methods is not recomended as it only works for measure objects and may result in inefficienies in processing the query. This resolution works the same for chasm and fan traps.

you can create more alias tables based on your requirement in single universe. and it is true conext, when two or more paths.

Theese methods also apply for resolving loops:

Short cut join also one method for resolving loops

Aggregate aware function used another waty for resolving loops

if you are not resolving the loop result is  redusing the number of records.

[Former Member]

Hi Khasim,

                  Let me know if you need any information regarding this

Regards

Dinesh

[Former Member]

Hi Khasim,

               It depends on what kind of schema you are using. If your universe schema has only one fact table than you can go for alias, but make sure there should not be many alias tables. That will ultimately confuse yourself and the rest of the designers later.

               If your schema has more than one fact table then you can go for context, but while using context you have to make sure the path used for context name should give the specific business meaning. Again there is a disadvantage of using context. The end users might get confuse which context to use for reports.

               In some cases we can also use short cut joins and agregate aware function to avoid loops rather than aliases and contexts.

If fact tables are less it is better to use alias for loops.

No other methods are there to resolve loops.

Please check the documentation:

http://help.sap.com/businessobject/product_guides/boexir4/en/xi4sp6_info_design_tool_en.pdf#page=120

And posts in internet, e.g.:

http://www.dagira.com/2009/07/22/context-versus-alias-overview/

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