Level Based Measure in OBIEE

A level-based measure is a column whose values are always calculated to a specific level of  aggregation. For example, a company might want to measure its revenue based on the country, based on the region, and based on the city. You can set up columns to measure CountryRevenue, RegionRevenue, and CityRevenue.

To set up these calculations, you need to build a dimensional hierarchy in your repository that contains the levels Grandtotal, Country, Region, and City. This hierarchy will contain the metadata that defines a one-to-many relationship between Country and Region and a one-to-many relationship between Region and City. For each country, there are many regions but each region is in only one country. Similarly, for each region, there are many cities but each city is in only one region.

Next, you need to create the logical column CountryRevenue in fact table  in BMM layer.
Right click on the fact table -> New Object -> Logical Column.

Then, Give a name to the measure, then under Aggregation tab, select the appropriate aggregation rule(SUM is the Aggregation for the measure CountryRevenue, in my case), then under the Level tab, select the appropriate logical level (country is the logical level for the measure CountryRevenue, in my case). Then say OK.

Repeat the same process for the other tow measures (RegionRevenue, and CityRevenue).

Now map the these logical measures to the physical source (Revenue is the physical source for these measures in my case.) To map the column CountryRevenue to the physical source column Revenue, follow the below steps :

Double click on the measure, called CountryRevenue, goto Data Type.You will find the logical Table source, double click on it.

Uncheck the option Show Mapped Columns, then all the unmapped columns will be displayed. In our case CountryRevenue,RegionRevenue, and CityRevenue are the unmapped columns. So, you should be able see all these columns there.

Now click on the dotted button (highligted in above picture) beside the measure CountryRevenue to map to physical source column. Then select the appropriate phisical source column from the Expression Builder and say OK.

Repeat the same procedure for other two columns.

Final step is, make sure that all the three measures should be listed under the corresponding logical Level in the dimension. In my case, the CoutryRevenue must listed under Country logical level, RegionRevenue must listed under Region logical level, CityRevenue must listed under City logical level in the dimension Product.

These measures are specific to the defined logical level. So CountryRevenue measure will always gives us the Revenue to the Country level, even if you add the Region dimension column in between Country and CountryRevenue  columns. RegionRevenue measure will always gives us the Revenue to the Country level, even if you add the City dimension column in between Region and RegionRevenue  columns.CityRevenue measure will always gives us the Revenue to the City level.

Thank you,

Disable the CAche Hit to Query Cache for a particular Request.

We can disable the Cach Hit for a particular request, by overriding/Change the value of System session variable called DISABLE_CACHE_HIT  to 1 in Answers.

Bypass Oracle BI Presentation Services Cache

We can By pass the presentation cach, by selecting the check box option for Bypass Oracle BI Presentation Services Cache in Advanced tab of any Answers.

Manipulating Session Variables from Answers

As my knowledge, session variables can be manipulated in Answers or dashboard of Presentation services in two possible ways.

• Request Variable
• NQSSetSessionValue 

 Request Variable

A request variable is a variable that is used to temporarily override the value of a session variable. The request variables are defined in the Presentation Services using either :

• Dashboard prompts or
• SET VARIABLE statement.

A variable whose name should not match that of a repository variable or a security system session variable(USER, GROUP etc..).

Using request variables we can change the value of session variables for any request or for all requests in any dashboard. But we can not change the value permanently through out the session. If we want to change the value of session variable for the entire session, then we can use the ODBC function NQSSetSessionValue. To know how to use request variable in presentation services, Click Here >>.

NQSSetSessionValue 

NQSSetSessionValue is an ODBC function, can be used to change the value of session variable for the whole session.

The syntax for this function is : 

                                               call NQSSetSessionValue('DataType VariableName=Value;')

We can call this function from from Issue SQL Directly section of Presentaion Services. To know how to use request variable in presentation services, Cick Here >>.

Error : [nQSError: 13015] You do not have the permission to set the value of the variable

View Display Error

Error getting drill information: SET VARIABLE LOB='APD' SELECT item.item saw_0, valueof(nq_session.LOB) saw_1 FROM OLEM   Error Details Error Codes: YQCO4T56:OPR4ONWY:U9IM8TAC:OI2DL65P Odbc driver returned an error (SQLExecDirectW). State: HY000. Code: 10058. [NQODBC] [SQL_STATE: HY000] [nQSError: 10058] A general error has occurred. [nQSError: 13015] You do not have the permission to set the value of the variable 'LOB'. (HY000) SQL Issued: {call NQSGetLevelDrillability('SET VARIABLE LOB=''APD'' SELECT item.item saw_0, valueof(nq_session.LOB) saw_1 FROM OLEM')}

 This is the common error, the developers get, when he try to change the value of session variable using request variable in request prefix field. ( refer how to change the value of session variable using Request Variable ).

Solution :
 Go to properties of session variable all check the option "Enable everyone to set value"

Follow the below steps :

1. Open Administration Tool. Go to Manager > Variables.

2. Select System or Non-System variable (depends on type of your variable) under the Session  from left pane. Then the corresponding variables will be listed on right pane.

3. Right click on the variable(for which your getting error in presentation service when you tried to change its value) and select properties.

4. check the option "Enable everyone to set value" (by default this option is unchecked) and click OK.

Now, check the request in presentation service. Log out from that session and again login to presentation services and the same report. If you get the same error again, please let me know by your comments.

NQSSetSessionValue - ODBC function

NQSSetSessionValue() is an ODBC function, can be used to change the value of session variable for the entire    session (ie. not only for a particular request or a dashboard).

The syntax for this function is : 

                                               call NQSSetSessionValue('DataType VariableName=Value;')

We can call this function from from Issue SQL Directly section of Presentaion Services.

Example :

Assume that, a user logon to the system, he has the value 2 for the session variable LOGLEVEL. If the user decides to increase the value for LOGLEVEL for the entire session. Then he can use the ODBC function to change the value of  LOGLEVEL.

Request Varaiable in OBIEE

A request variable is a variable that is used to temporarily override the value of a session variable. The request variables can be defined in two places of Presentation Services, as my knowledge.

• Dashboard prompts or
• SET VARIABLE statement.

A variable whose name should not match that of a repository variable or a security system session variable(USER, GROUP etc..).

  

Request Variable in a Request : 

 We can define Request Variables in any request to override the session variable, using the SET VARIABLE code. When we define a request variable for any request, then the scope and availability of that variable is within the same request. Outside of this request, the session variable will be having the actual value, not the overridden value.

 Example :  Assume that there is a session variable called LOB  and someone logged into the presentation services, for this session the value of LOB is 'APD'. Then he can change this value for any particular request using the following steps :

Before request variable, the session variable LOB has the value 'APD'.

To change the value of LOB to the value 'Liability', Go to Advanced tab of Answers.

Go down and find the PREFIX clause, and write the following code in that.

 Then Click on Result tab and check the result. Now you will find the changed value Liability.

The request variable overrides the value of session variable only for this request, the session variable will have the actual value 'APD' outside of this request.

Request Variable in Dashboard Prompt  

We can use Request variable in Dashboard prompts to change the value of session variable. The scope of this variable would be Page of Dashboard, depends on the selection.  

Example : Lets use the same session variable LOB (which we used for request) for this example. 

The below request have used the session variable LOB and value of this variable for the current session is 'APD'.

In dashboard prompt,  take the required logical column, select Request Variable from Set Variable drop-down and write the request variable name, LOB is in our case. 

Put the same report and dashboard prompt into the dashboard.

Now select any value from prompt and click on Go.

In my case, I have selected the value 'Property'. The request variable, changed the default value of session variable to the selected value( from prompt).

If we have more than one request in the dashboard, the same will be affected for all the requests in that  dashboard. Outside of this dashboard, the value of the session variable will be the actual value only.

Note : Using a request variable does not change the actual value of a session variable – neither temporarily nor permanently.  It simply appears to change the value for certain purposes during the execution of a request.

To know more about Request Variable, like how it works, what actually it is, Please refer the following link.
http://everythingoracle.com/obieerv.htm

Thank you,

Variables in the Oracle BI Repository

There are two classes of variables:

1. Repository variables (Server Variables): holds the same value across all sessions

2. Session variables: holds a value specific to each user session.

Caution:

Values in repository and session variables are not secure, because object permissions do not apply to variables. Anybody who knows or can guess the name of the variable can use it in an expression in Answers or in a Logical SQL query. Because of this, do not put sensitive data like passwords in session or repository variables.

Repository variables: 

A repository variable has a single value at any point in time, I.e., holds the same value across all sessions. Repository variables can be used instead of literals or constants.

There are two types of repository variables:

1.  Static Repository Variables

2. Dynamic Repository Variables.

Static  Repository Variables: 

Static repository variables holds constant values for all sessions in the server. This value persists, and does not change until an administrator decides to change it.

Assume that, you are using a value 'California' (head office of client) very often in formula of reports or in Expression Builder of BMM layer in repository. Then instead of using direct value, we can assign this constant value to a static variable and use this variable wherever required. That will be more understandable to users than direct values.

Lets create a static repository variable called HEAD_OFFICE.

1. In the Administration Tool, select Manage > Variables.

Select Static from left pane, then right click on the right pane of the Variables and select New Static variable.

In the Variable dialog, type a name(HEAD_OFFICE in our case) for the variable.

Names for all variables should be unique. The names of system session variables are reserved and cannot be used for other types of variables. 

To add a Default initializer value, type the value in the Default initializer box, or click the Expression Builder button to use Expression Builder.

If you initialize a variable using a character string, enclose the string in single quotes ( ' ). Static repository variables must have default initializers that are constant values.

Type the value  'California' in the Default initializer box for our case.

3.      Click OK.

Now, to see all the static variables in the server, select Static under Variables in Variable manager, then you can see all the static variables in right pane.

Dynamic  Repository Variables: 

These variables can have values that vary over time . 

When defining a dynamic repository variable, you create an initialization block. You also set up a schedule that the Oracle BI Server will follow to execute the query and periodically refresh the value of the variable.

When the value of a dynamic repository variable changes, all cache entries associated with a business model that reference the value of that variable are purged automatically.

Dynamic repository variables are useful for defining the content of logical table sources. For example, we need to refer count of employee in some places, and then we can create a dynamic variable called COUNT_OF_EMP and schedule it to every 1 day (because a new employee may join on any day).

To create a repository variable:

Lets create a Dynamic variable called  COUNT_OF_EMP, we have table called Emp. The query to get count of employees is : select count( distinct empkey) from EMP.

1. In the Administration Tool, select Manage, then select Variables.

2. In the Variable Manager dialog, select dynamic from left pane and right click on right pane, then  select New Dynamic Variable.

3. In the Variable dialog, type a name for the variable.

Names for all variables should be unique. The names of system session variables are reserved and cannot be used for other types of variables.

4.  To create a new initialization block, click New.

5.      In Repository Init Block dialogue, set the initialization block name, schedule the refresh interval(in my case I have given 1 hour as refresh interval. So the BI server will send the query to database and get the data for every one hour). 

Notice that in our case, I have scheduled the variable refresh interval  to one hour. So the value of this variable will be refreshed for every hour by the BI Server.

6.      Next, click on the Edit Data Source, write the SQL Query, select the Connection Pool and click on OK.

7.      Next click on Edit Data Target, and define the Dynamic Variables and click on OK.

8.   Click OK.

Session Variables :
Session variables are similar to dynamic repository variables in that they obtain their values from initialization blocks. Unlike dynamic repository variables, however, the initialization of session variables is not scheduled. When a user begins a session, the Oracle BI Server creates new instances of session variables and initializes them.

Unlike a repository variable, there are as many instances of a session variable as there are active sessions on the Oracle BI Server. Each instance of a session variable could be initialized to a different value.

Session variables are primarily used when authenticating users against external sources such as database tables or LDAP servers. If a user is authenticated successfully, session variables can be used to set filters and permissions for that session.

Session Variables can be further classified as :
• System Session Variables
• Nonsystem Session Variables
System Session Variables
System session variables are session variables that the Oracle BI Server and Oracle BI Presentation Services use for specific purposes. System session variables have reserved names that cannot be used for other kinds of variables (such as static or dynamic repository variables and nonsystem session variables).

When you use these variables for Oracle BI Presentation Services, preface their names with NQ_SESSION. For example, to filter a column on the value of the variable LOGLEVEL, set the filter to the variable NQ_SESSION.LOGLEVEL.

Variable	Description
USER	Holds the value the user enters as his or her logon name. This variable is typically populated from the LDAP profile of the user.
PROXY	Holds the name of the proxy user. A proxy user is a user that has been authorized to act for another user. See Oracle Fusion Middleware System Administrator's Guide for Oracle Business Intelligence Enterprise Edition for more information about the PROXY system session variable.
GROUP	Contains the groups to which the user belongs. Exists only for compatibility with previous releases. Legacy groups are mapped to  application roles automatically.
WEBGROUPS	Specifies the Catalog groups (Presentation Services groups) to which the user belongs, if any. Note that the recommended practice is to use application roles rather than Catalog groups.
USERGUID	Contains the global unique identifier (GUID) of the user, typically populated from the LDAP profile of the user.
ROLES	Contains the application roles to which the user belongs.
ROLEGUIDS	Contains the global unique identifiers (GUIDs) for the application roles to which the user belongs. GUIDs for application roles are the same as the application role names.
PERMISSIONS	Contains the permissions held by the user, such as oracle.bi.server.impersonateUser or oracle.bi.server.manageRepository.
DISPLAYNAME	Used for Oracle BI Presentation Services. It contains the name that  is displayed to the user in the greeting in the Oracle BI Presentation  Services user interface. It is also saved as the author field for catalog objects. This variable is typically populated from the LDAP  profile of the user.
PORTALPATH	Used for Oracle BI Presentation Services. It identifies the default dashboard the user sees when logging in (the user can override this  preference after logged on).
LOGLEVEL	The value of LOGLEVEL (a number between 0 and 5) determines the logging level that the Oracle BI Server uses for user queries. This system session variable overrides a variable defined in the Users object in the Administration Tool. If the administrator user (defined upon install) has a Logging level defined as 4 and the session variable LOGLEVEL defined in the repository has a value of 0 (zero), the value of 0 applies.
REQUESTKEY	Used for Oracle BI Presentation Services. Any users with the same  nonblank request key share the same Oracle BI Presentation Services cache entries. This tells Oracle BI Presentation Services that these users have identical content filters and security in the Oracle BI Server. Sharing Oracle BI Presentation Services cache entries is a way to minimize unnecessary communication with the Oracle BI Server.
SKIN	Determines certain elements of the look and feel of the Oracle BI Presentation Services user interface. The user can alter some elements of the user interface by picking a style when logged on to Oracle BI Presentation Services. The SKIN variable points to an Oracle BI Presentation Services folder that contains the nonalterable elements (for example, figures such as GIF files). Such directories begin with sk_. For example, if a folder were called sk_companyx, the SKIN variable would be set to companyx.
DESCRIPTION	Contains a description of the user, typically populated from the LDAP profile of the user.
USERLOCALE	Contains the locale of the user, typically populated from the LDAP profile of the user.
DISABLE_CACHE_HIT	Used to enable or disable Oracle BI Server result cache hits. This variable has a possible value of 0 or 1.
DISABLE_CACHE_SEED	Used to enable or disable Oracle BI Server result cache seeding. This variable has a possible value of 0 or 1.
DISABLE_SUBREQUEST_CACHE	Used to enable or disable Oracle BI Server subrequest cache hits and seeding. This variable has a possible value of 0 or 1.
SELECT_PHYSICAL	Identifies the query as a SELECT_PHYSICAL query. See "Syntax and Usage Notes for SELECT_PHYSICAL" for more information.
DISABLE_PLAN_CACHE_HIT	Used to enable or disable Oracle BI Server plan cache hits. This variable has a possible value of 0 or 1.
DISABLE_PLAN_CACHE_SEED	Used to enable or disable Oracle BI Server plan cache seeding. This variable has a possible value of 0 or 1.
TIMEZONE	Contains the time zone of the user, typically populated from the LDAP profile of the user.

Nonsystem Session Variables

You use the same procedure to define nonsystem session variables as for system session variables.

A common use for nonsystem session variables is setting user filters. For example, you could define a nonsystem variable called SalesRegion that would be initialized to the name of the sales region of the user.

You could then set a security filter for all members of a group that would allow them to view only data pertinent to their region.

When you use these variables for Oracle BI Presentation Services, preface their names with NQ_SESSION. For example, to filter a column on the value of the variable SalesRegion, set the filter to the variable NQ_SESSION.SalesRegion.

Creating Session Variables

1. In the Administration Tool, select Manage, then select Variables.
2. In the Variable Manager dialog, select Action > New > Session > Variable.
3. In the Session Variable dialog, type a variable name.
   Names for all variables should be unique. The names of system session variables are reserved and cannot be used for other types of variables.
4. For session variables, you can select the following options:
• Enable any user to set the value. Select this option to set session variables after the initialization block has populated the value (at user login) by calling the ODBC store procedure NQSSetSessionValue() or by using Request variable. For example, this option lets non-administrators to set this variable for sampling.
5. Use the Initialization Block list to select an initialization block that will be used to refresh the value on a continuing basis.
6. To add a Default Initializer value, type the value in the Default Initializer box, or click the Expression Builder button to use Expression Builder.
7. Click OK.

Syntax for using these variables :
Repository variables can be used in two ways : 
1. VALUEOF(variable name) 
2. biServer.variables['variable name']



Session variables can be used in two ways : 
1. VALUEOF(NQ_SESSION.variable name) 
2. biServer.variables['variable name']

All Types Of Variables in OBIEE

Mainly, There are two types of variables in OBIEE.

1. Presentation  Variables

2. Server-Side Variables (Session and Repository variables)

3. Request Variables

Presentation  Variable  is the only variable offer by the presentation service, used to pass value between dashboard prompt and to set some filter in Presentation Services.You can set it with the help of the dashboard prompt which will then take the data type of the presentation column.The scope of a presentation variable depends of the prompt scope. The prompt scope may be dashboard or page. If we select score of prompt as dashboard then the variable will be available in all pages of dashboard. Whereas if we select scope as page, then the variable will be available in the same page.

Server-Side variables are create and initialize in Repository. There are two types in this :

1. Repository variables

2. Session Variables.

A repository variable has a single value at any point in time, I.e., holds the same value across all sessions. Repository variables can be used instead of literals or constants.

There are two types of repository variables:

1.  Static  Repository Variables

2. Dynamic Repository Variables.

A session variable is a variable that is initialized at login time for each user. When a user begins a session, the Oracle BI Server creates a new instance of a session variable and initializes it.

There are as many instances of a session variable as there are active sessions on the Oracle BI Server. Each instance of a session variable could be initialized to a different value.

There are two types of session variables:

1. System session variable

2. Non-System session variable.

To read more about these variables Click Here.

A request variable is a variable that is used to temporarily override the value of a session variable.It is defined within the Presentation Services. A request variable name should not match that of a repository variable or a security system session variable(we cant override values of variables like USER, GROUP, LOGLEVEL etc.).  To read more about request variables Click Here.

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In BMM layer of Administration tool, if you do not define logical join for a logical table, the following error will occur.

Solution : Identify the Logical table in the Error message, and make the proper joins in BMM layer.

[nQSError: 14026] Unable to navigate requested expression

When the joins are not properly defined in Physical layer for a physical table then the following error will results by Presentation services when we request the same table.

Solution :

Open Administrator Tool, find the physical table which you used in the request, define the joins with the fact/dimensional table properly. Then save the repository and restart the services (presentation services and BI services) or reload the metadata. Now check the same request in presentation services.

Logical SQL in OBIEE

Logical SQL is the SQL that can understand by OBI Server.When a user requests data, then the presentation services server prepares a Logica SQL and send it to OBI Server to retrieve dataset.The Oracle BI Server transforms the Logical SQL into physical SQL through a process known as query processing that can be understood by source databases.

In Presentation Service, when you create an answer or a dashboard prompt, you create in fact a logical SQL that you can see in the Advanced Tab of the answer

Complex Join and Physical/Foreign Key Join

Physical/Foreign Key Join

A Physical/Foreign Key  repository join is used only to define a Primary Key-Foreign Key Relationships in the Physical Layer. When you create  Primary Key-Foreign Key Relationships  in the physical diagram, you have to point first the dimension and then the fact table.

Tip : While importing tables from physical schema into RPD, if we select KEY and FOREIGN KEY along with the table, then the primary key-foreign key joins are automatically defined. But this is not a good practice. We should not import keys and foreign keys as it takes long time if we have more data in tables and more tables in schema.

Complex Join :

In the business model, OBI recommends using complex logical joins instead of foreign key logical joins.

When Complex joins are used in the business layer then they are really acting as placeholders. 

They allow the OBI Server to decide on which are the best joins define in the Physical Layer to satisfy the request.

In a Dimension, you may have multiple Logical Table sources that all join to one fact table. The OBI Server will then decide the best joins to use to meet the requirements.

Shared Logon In Connection Pool

The Username and Password fields under the Shared Logon option in Connection Pool properties, allows the Administrator to specify the USERNAME and PASSWORD of the underlying Database.

Select the Shared logon check box if you want all users whose queries use the connection pool to access the underlying database using the same user name and password.

If this option is selected, then all connections to the database that use the connection pool will use the user name and password specified in the connection pool, even if the user has specified a database user name and password in the DSN (or in user configuration).

If this option is not selected, connections through the connection pool use the database user ID and password specified in the DSN or in the user profile.

Fragmentation in OBIEE

We use fragmentation when we have fact or dimensional data in one or more different tables or data is splitted in different data sources. Then each logical table source represents one data segment.

For example, clients, in the first table are clients from A to M, in the second from M to Z.

Fragmentation of dimension

If our dimensional data is located on two or more physical tables in database (tables) or it is on separeted data sources then we can handle this by using UNION ALL views in physical layer.

However for testing this option we'll simulate this by using CHANNELS table. So we splitt it to a table CHANNELS_OTHER and CHANNELS. Fragmentation attrubur is CHANNEL_ID.

In our SALES fact table that we used here we use CHANNEL_ID from both tables CHANNELS and CHANNELS_OTHER.

Physical model, join:

SALES.CHANNEL_ID >- CHANNELS.CHANNEL_ID
SALES.CHANNEL_ID >- CHANNELS_OTHER.CHANNEL_ID

BMM:

Settings:


Test in Answers:

Result:

NQQuery.log:

We see that UNION ALL is generated.

If we choose:

NQQuery.log:

We see that the SQL is using only the second fragmented logical table source and the condition is applied only for that logical table source.

If we choose:

NQQuery.log:

If we now choose any other attribut (CHANNEL_CLASS) that is not CHANELL_ID which we used as a fragmentation key:

Then this condition is applied on both logical table sources CHANNEL and CHANNEL_OTHER:

Fragmentation of fact table

Let's split data for SALES 1998 in separate table SALES_HIST. Data from 1998 we leave in SALES.

Physical model, join:

SALES.TIME_ID >- TIMES.TIME_ID
SALES_HIST.TIME_ID >- TIMES.TIME_ID

BMM:

Settings (for a fragmentation key we choose CALENDAR_YEAR):


Test in Answers:

Result:

NQQuery.log:

If we choose:

NQQuerylog:

If we choose:

NQQuery.log:

If we now choose any other attribut (CALENDAR_MONTH_DESC) that is not CALENDAR_YEAR which we used as a fragmentation key:

Then this condition is applied on both logical table sources SALES and SALES_HIST:

In this post we showed how to combine different sources of information using fragmentation option. We see that at any moment we can see which source OBIEE takes while generating code.