Hyperion Essbase Interview Questions

Hi,
You may also like to read Essbase Interview Questions.

I have got this request from someone to post some FAQ's on Hyperion Essbase. Please do not just rely on these questions only. I recommend you read the Essbase documentation and get some hands on to understand the basics. The questions below shold guide you to narrow down your search for the topics you should focus on.

Que 1: What are the two storage options available in Essbase and what are the differences?
Ans: ASO( Aggregate Storage Option) - Used for 1. If we have large number of dimensions(generally more than 10) 2. Most of the dimensions are sparse 3. We cannot write back in ASO. I heard recently that ASO will also have the writeback capability. I don't remember.
BSO (Block Storage Option)- 1. Dimensions are less and dense(recommended values for no of dim are between 4 and 8) . 2. We can write back hence much suited for planning applications.
Financial applications are generally dense structures and normal analytical cubes are sparse. Here we also need to understand what are these dense and sparse members. When the intersections or cells of two dimensions mostly contains a value it is dense. Say for example we have two dimensions period(Month or quarter) and region and we are calculation the sales amount. Generally maximum regions(countries, cities) will have some sales value for a particular month or quarter. Hence we can say that our period dimensions would be dense. But now instead of period, consider another dimension products. Now there are some products which are sold in only some particular regions hence for them there will be no values in other regions or will have very low percentage of data values hence the structure will become sparse.
Now the question arises what is the use of calling them dense or sparse. What difference does it make. Do some research and try to find the answer.


Que 2: Can we build dimensions directly from data sources without using rule files.
Ans: No.

Que 3: When do we generally use build rules files?
Ans: To automate the process of creating dimensions with thousands of members.

Que 4: What are the three primary build methods for building dimensions?
Ans: 1. Generation references
2. level references
3. Parent-Child references.

Que 5: In what case we can define generation 1 to a feild in generation build method.
Ans: We cannot define that as Generation 1 is not valid.

Que 6: Suppose we have assigned Generation 2 and Generation 4 as of now and think of adding generation 3 later some time. Can we build the dimension.
Ans: No. If gen 2 and gen 4 exists, we must assign gen 3.

Que 7: Can we create more than 2 dimensions using only one build rule file.
Ans: Yes, we can do that but it is recommended to use seperate rule file for each dimension.

Que 8: What is UDA( user defined attributes). How are they different than Aliases.
Ans: UDA represents the class of the members. Aliases are just another names of the members. both are different and has different usage.

Que 9: Can we query a member for its UDA in a calculation script.
Ans: Yes. You can query a member for its UDA in a calculation script.

Que 10: How does UDA's impact database size?
Ans: Absolutely no impact as UDA's do not require additional storage space.

Que 11: What is the difference between UDA's and Attribute dimensions?
Ans : Attribute dimensions provides more flexibility than UDA's. Attribute calculations dimensions which include five members with the default names sum, count, min, max and avg are automatically created for the attribute dimensions and are calculate dynamically.

Que 12: How does Attribute dimensions and UDA's impact batch calculation performance?
Ans: UDA's- No Impact as they do not perform any inherent calculations.
Attribute dim- No Impact as they perform only dynamic calculations.

Que 13: How can we display UDA's in reports? How do they impact report report performance.
Ans: UDA's values are never displayed in the reports and hence do not impact report performance.

Que 14: How does Attribute dim impact report performance?
Ans: They highly impact the report performance as the attributes are calculated dynamically when referenced in the report. For very large number of att dim displayed in the report, the performance could drastically reduce.

Que 15: While loading the data, you have applied both the selection criteria as well as rejection criteria to a same record. What will be the outcome.
Ans: Thw record will be rejected.

Que 16: How is data stored in the Essbase database?
Ans: Essbase is an file based database where the data is stored in PAG files of 2 GB each and grows sequentially.

Que 17: Can we have multiple databases in one single application?
Ans: Yes. But only one database per application is recommended.

Que 18: Can we have one ASO database and one BSO database in one single application. If yes, how and If No, why.
Ans 18. No. Because we define ASO or BSO option while creating the appication and not database. Hence if the application is ASO, the databases it contains will be that type only.

Que 19: What are the file extensions for an outline, rule file and a calc script.
Ans: .OTL, .RUL and .CSC

Que 20: What is the role of provider services.
Ans: To communicate between Essbase and Microsoft office tools.

Que 21: What is an alternative to create metaoutline, rule file and load data.
Answer: Integration services and in version 11, we have Essbase studio.

Que 22: Can we start and stop an application individually. How ca this be used to increase performance.
Ans: Yes. We can manage our server resources by starting only the applications which receive heavy user traffic. When an application is started, all associated atabases are brought to the memory.

Que 23: We have created an application as unicode mode. Can we change it later to non-unicode mode.
Ans: No.

Que 24: How can I migrate an application from my test environment to the production environment. Can I still do this if my test environment is a windows one and my production env is UNIX one. Also can I still do it if my test env and prod env versions are different.
Ans: Hyperion Administrative services console provides a migration utility to do this but onluy the application, database objects are migrated and no data is transferred. the answers to other two questions are Yes.

Que 25: A customer wants to run two instances of an Essbase server on a same machine to have both test env and Development env on the same server. Can he do that?
Ans: Yes. We can have multiple instances of an Essbase server on a single machine and there will be dfferent sets of windows services for all these instances.

Que: 26 suppose I have a dimension A with members B and C and I do not want B and C to roll up to A. how can I do this.
Ans: Using (~) exclude from consolidation operator.

Que 27: What does never consolidate operator(^) do?
Ans: It prevents members from being consolidate across any dimension.

Que 28: Can we have multiple metaoutlines based on one OLAP model in Integration services?
Ans: Yes

Que 29: Can we have an metaoutline based on two different OLAp models.
Ans: No.

Que 30: What is hybrid analysis?
Ans: Lower level members and associated data remains in relational database where as upper level members and associated data resides in Essbase database.

Que 31: Why top-down calculation less efficient than a bottom-up calculation?Being less efficient, why do we use them.

Ans: In the process it calculates more blocks than is necessary. Sometimes it is necessary to perform top-down calculation to get the correct calculation results.

Que 32: On what basis you will decide to invoke a serial or parellel calculation method.

Ans: If we have a single processor, we will use serial calculation but if we have multiple processors we can break the task into threads and make them run on different processors.

Que 33: What is block locking system?

Ans: Analytic services(or Essbase Services) locks the block and all other blocks which contain the childs of that block while calculating this block is block locking system.

Que 34: What are the types of partitioning options available in Essbase?

Ans: 1. Replicated partition. 2. Transparent partition 3. Linked partition.

Que 35: Dynamic calc decreases the retreival time and increases batch database calculation time. How true is the statement?

Ans: The statement should be just opposite. As dynamic calc members are calculated when requested, the retreival time should increase.

Que 36: A customer has a cube with 13 dimensions and the performance was fine. Now they have added two more dimensions in the existing cube and the performance becomes very very slow. Customer said logically nothing wrong with the two new dimensions they have added. What could be the reason for slowdown.

Ans: Even I dont have any clue. I experienced this few days back with a customer. If you can throw some light on this, please post your answer.

If you have more questions with answers, please post them so that all of us can benefit.

Also let me know your views and suggestions.

Manohar Rana