Friday, 19 August 2016

OBIEE RPD Interview Questions

OBIEE RPD Interview Questions:

Physical Layer : 
1. What is connection pool?
  1.  Connection pool is a physical layer object, is useful to store data base credentials like database name, username, password etc.
  2.  OBIEE oracle BI Server contacts data base using connection pool
2. How to import views/materialized views?
         While importing we need to enable views option
3. What is the isolation level in a connection pool?
  1. It applies only For ODBC and DB2 gateways only. The value sets the transaction isolation level on each connection to the back-end database. The isolation level setting controls the default transaction locking behaviour for all statements issued by a connection. Only one option can be set at a time. It remains set for that connection until it is explicitly changed.
  2. The following options are available:
    1. Dirty read. Implements dirty read (isolation level 0 locking). This is the least restrictive isolation level. When this option is set, it is possible to read uncommitted or dirty data, change values in the data, and have rows appear or disappear in the data set before the end of the transaction. Dirty data is data that needs to be cleaned before being queried to obtain correct results (for example, duplicate records, records with inconsistent naming conventions, or records with incompatible data types).
    2. Committed read. Specifies that shared locks are held while the data is read to avoid dirty reads. However, the data can be changed before the end of the transaction, resulting in non-repeatable reads or phantom data.
    3. Repeatable read. Places locks on all data that is used in a query, preventing other users from updating the data. However, new phantom rows can be inserted into the data set by another user and are included in later reads in the current transaction.
    4. Serializable. Places a range lock on the data set, preventing other users from updating or inserting rows into the data set until the transaction is complete. This is the most restrictive of the four isolation levels. Because concurrency is lower, use this option only if necessary.
4. How many connection Pools you used in your project
1. It is a general question, there is no fixed answer, and however in each project we will have minimum three connection pools
  1. One for importing tables  and execute reports
  2. One for execute session initialization block sql queries
  3. One for usage tracking purpose
2. Recommended number is between 2 to 10.but justification is important.
5. To get data of another schema, then what we need to enable in connection pool
1.       Required fully qualified names
2.       DB permissions
6. Can we create multiple connection pools under one database object?
Yes, we can
7. What is the difference between Duplicate and Alias in physical layer?
1.        We will use Alias in physical layer to resolve below problems
1.       Self-Join
2.       To maintain naming Standards in physical layer
3.       Resolve loops or closed paths
2.       Duplicate normally used in Physical layer  to create a duplicate copy of existing Select table (Opaque View)  /stored Procedure object
8. How many types of Joins are there in Physical layer?
          Two types
1.        Foreign Key join
1.       Equivalent to Equi join
2.       Accepts only = operator
3.       Most used join in physical layer
2.        Complex Join
1.       Equivalent to Non Equi join
2.       Accepts all operators like (=,<>,=>,,=…….etc)
3.       Less used join in Physical layer
9. Can we create self-join?
By using Alias table, we can create self-join.
10. Can we create outer join in physical layer.
In Physical Layer Outer join not possible, however we can create outer join in BMM layer.
11. How to remove unused objects from physical layer
  1.  It will remove objects, which we did not use in BMM layer
  2. Tools menu | Utilities | Remove unused objects from physical layer
12. How to synchronize physical layer objects
  1. It is useful to synchronize RPD metadata with DB metadata
  2. Tools | Utilities | Update Physical Layer
13. What is complex join, in which scenario we use it.
  1.  If foreign key is not possible then we will go for complex join. For example between emp and salgrade we will use complex join
  2. In place of non equi join ,complex join is used
14. In foreign key join can we use other than equal to operator?
No
15. What is Opaque View?
1.       A SQL query or select statement is called as opaque view.
2.       If we need a new table then go for physical table (or) materialized view. In worst situation go for opaque view.
3.       Opaque views are not supported by non-relational db.(example MS Excel ,XML ,ESSBASE …etc)
4.       If we need to call data base function then we have to go for Opaque View.
16. Is deploying opaque is mandatory?
1.       No. but it is recommended due to below reason
2.       Without deploying view into database, if we use opaque view in reports then oracle BI server needs to create complex queries. To avoid complex queries oracle recommended to deploy each and every opaque view into database.
17. When automatic joins will be created in physical layer.
If we have primary key and foreign Key relationship in database level and while importing if we enable foreign key options then automatic joins will be created.
18. What is Alias?
1.       A virtual physical table (or) reference of physical table is called as alias.
2.       On one physical table we can create ‘n’ no. of aliases.
3.        Whatever changes occurred in physical table that will immediately reflect in alias (except Key definitions)
4.       It is mainly useful to resolve loops
19. Can we create or delete a column from Alias.
No
20. How to eliminate Circular Join or loop or closed path.
By Using Alias


BMM Layer :
1. What is the business model?
  1. Is the highest-level object in the BMM layer
  2. Contains the business model definitions and the mappings from logical to physical tables
  3. Simplifies the physical schema
  4. Captures how users think about their businesses using their own vocabulary
2. Can we create business model with single logical table, if no please let me know work around.
  1. Approach 1: Creating duplicate table in BMM layer
  2. Approach 1: Creating alias and creating join between original table and alias
3. Can we create business model from multiple databases, did you created then tell me one scenario
Yes, Scenario: when we want to compare the Actual data with target data and these data coming from sources like oracle database and MS-Excel respectively 
4. What is the Logical Table Source and when we will go for multiple logical tables
1.       Logical table sources define the mappings from single logical table to one or more physical tables.
2.       A logical table contains one or more logical table source.
3.       The mapping between physical columns and logical columns can manage using LTS
4.       By integrating multiple physical tables to LTS or  By integrating multiple LTS to LT we can convert snow flake schema into star schema 
5. When we need to integrate multiple physical tables in LTS.
If we have snowflake schema then want to convert that into star schema then we will go for multiple logical tables.
6. Did you get chance to map a logical column with multiple physical columns
Yes, If we want to configure aggregate tables then we need to do it .
7. What is logical join and why it is useful?
 The join defined in the BMM Layer is called logical join
1.       Logical join is used to defined driving table
2.       Logical Join is used to define Inner, Right, Left and Full outer joins
3.       Used to defined the cardinality
4.       Logical join is useful to identify dimension and fact table
5.       Logical join allows Oracle BI Server to make the best decision about the exact physical SQL to generate based on the logical query path.
8. Can we have a table without logical join?
No
9. Can we have a dimension table without primary key?
No
10. Can we copy RPD objects within the RPD and from one RPD to another RPD?
  1.  Yes, we can copy RPD objects with in the RPD.
  2. We can copy one RPD to another  RPD but we need to copy corresponding layers only i.e. (physical to physical, BMM to BMM and presentation to presentation)
11. What is Renaming wizard and which layers can be modified.
Renaming wizard is used to rename all objects (example: tables and columns) of BMM and Presentation layer

Presentation Layer : 

1. Can we create a subject area from multiple business models?

No
2. In which version of OBIEE, presentation layer supporting hierarchy object
OBIEE 11G
3. What is Aliases?
Keep track of any changes to Presentation layer objects
4. What are nested tables?
  1. Prefix the name of the presentation folder to be nested with a hyphen and a space. or type " - > "in description of the column 
  2. Place it after the folder in which it nests
5. Can we map a presentation column with multiple logical columns?
We can not

Testing and Validating Repository:

What is global consistency check?
  1. Consistency check is one of the processes to check whether a repository is yielding proper results in Answer reports. It checks whether;
    1. All logical columns are mapped correctly to physical columns.
    2. All logical dimension tables have a logical key.
    3. Are there at least two logical tables in the business model (one is a logical fact table and the other is logical dimension table with join condition).
    4. There are no circular logical join relationships.
    5. A presentation catalog exists for the business model.
  2. How many messages are there in consistency check manager?
    1. Up to OBIEE 11.1.1.5 version There are 3 messages in consistency check manager such as
      1.  Errors
      2. Warnings
      3. Best Practices 
    2. In OBIEE 11.1.1.6 version onwards There are 3 messages in consistency check manager such as
      1. Errors
      2. Warnings
  3. In OBIEE how many servers are there?
           In OBIEE 11G we have 6 servers
      1. Oracle BI Server
      2. Oracle BI Presentation server
      3. Oracle BI Java host server
      4. Oracle Oracle BI Scheduler server
      5. Oracle BI Cluster controller server
      6.  Web logic Server (newly added in OBIEE11G)
  1. What is OPMNCTL and how many servers are integrated in it.
    1. The Oracle Process Manager and Notification Server Control 
      1. Oracle BI Server
      2. Oracle BI Presentation server
      3. Oracle BI Java host server
      4. Oracle Oracle BI Scheduler server
      5. Oracle BI Cluster controller server
  2. NQSCONFIG.INI and NQSERVER.log files are corresponding to which server.
OBI server
  1. Can we load multiple RPDs in Oracle BI server
No, we can’t
  1. Can we upload RPD without using EM?
We can’t
  1. How many log levels are available
Totally 8 levels (0 to 7)
  1. What are the log levels in development, test and production, you used in your project.
    1. In Development  and Test we will use log level as 2
    2. In production we will use log level 0
  2. All query logs will be stored in which file and what is that file physical path
    1. NQQUERY.log file 
    2. C:\OBIEE_OBIEE\instances\instance1\diagnostics\logs\OracleBIServerComponent\coreapplication_obis1
  3. In log level 1 can we see physical SQL query.
    1. No, we cannot see the physical SQL query it shows logical SQL query.
    2. If you set logging level as 2 then it gives all log information of level 1 along with physical SQL query
  4. Global consistency check is not throwing any errors, then can we assume RPD is correct
Syntax wise it is correct .Business rules wise we may have some mistake 
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