Oracle ODI Interview Questions
Oracle ODI Interview Questions
What is Oracle Data Integrator (ODI)?
Oracle acquired SUNOPSIS with its ETL tool called "Sunopsis Data Integrator" and renamed to Oracle Data Integrator (ODI) is an E-LT (Extract, Load and Transform) tool used for high-speed data movement between disparate systems.
The latest version, Oracle Data Integrator Enterprise Edition (ODI-EE 12c) brings together "Oracle Data Integrator" and "Oracle Warehouse Builder" as separate components of a single product with a single licence.
Explain what is ODI?why is it different from the other ETL tools.
ODI stands for Oracle Data Integrator. It is different from another ETL tool in a way that it uses E-LT approach as opposed to ETL approach. This approach eliminates the need of the exclusive Transformation Server between the Source and Target Data server. The power of the target data server can be used to transform the data. i.e. The target data server acts as staging area in addition to its role of target database.
while loading the data in the target database (from staging area) the transformation logic is implemented. Also, the use of appropriate CKM (Check Knowldege Module) can be made while doing this to implement data quality requirement.
What is E-LT? Or What is the difference between ODI and other ETL Tools?
E-LT is an innovative approach to extracting, loading and Transforming data. Typically ETL application vendors have relied on costly heavyweight , mid-tier server to perform the transformations required when moving large volumes of data around the enterprise.
ODI delivers unique next-generation, Extract Load and Transform (E-LT) technology that improves performance and reduces data integration costs, even across heterogeneous systems by pushing the processing required down to the typically large and powerful database servers already in place within the enterprise.
Components of Oracle Data Integrator?
Oracle Data Integrator" comprises of:
- Oracle Data Integrator + Topology Manager + Designer + Operator + Agent
- Oracle Data Quality for Data Integrator
- Oracle Data Profiling
What systems can ODI extract and load data into?
ODI brings true heterogeneous connectivity out-of-the-box, it can connect natively to Oracle, Sybase, MS SQL Server, MySQL, LDAP, DB2, PostgreSQL, Netezza.
What are Knowledge Modules?
Knowledge Modules form the basis of 'plug-ins' that allow ODI to generate the relevant execution code , across technologies , to perform tasks in one of six areas, the six types of knowledge module consist of:
- Reverse-engineering knowledge modules are used for reading the table and other object metadata from source databases.
- Journalizing knowledge modules record the new and changed data within either a single table or view or a consistent set of tables or views
- Loading knowledge modules are used for efficient extraction of data from source databases for loading into a staging area (database-specific bulk unload utilities can be used where available)
- Check knowledge modules are used for detecting errors in source data
- Integration knowledge modules are used for efficiently transforming data from staging area to the target tables, generating the optimized native SQL for the given database
- Service knowledge modules provide the ability to expose data as Web services
- ODI ships with many knowledge modules out of the box, these are also extendable, they can modified within the ODI Designer module.
Does ODI support web services?
Yes, ODI is 'SOA' enabled and its web services can be used in 3 ways:
The Oracle Data Integrator Public Web Service, that lets you execute a scenario (a published package) from a web service call Data Services, which provide a web service over an ODI data store (i.e. a table, view or other data source registered in ODI)
The ODIInvokeWebService tool that you can add to a package to request a response from a web service
What is the ODI Console?
ODI console is a web based navigator to access the Designer, Operator and Topology components through browser.
what is load plans and types of load plans?
Load plan is a process to run or execute multiple scenarios as a Sequential or parallel or conditional based execution of your scenarios. And same we can call three types of load plans , Sequential, parallel and Condition based load plans.
What is profile in ODI?
Profile is a set of objective wise privileges. we can assign this profiles to the users. Users will get the privileges from profile
How to write the sub-queries in ODI?
Using Yellow interface and sub queries option we can create sub queries in ODI. or Using VIEW we can go for sub queries Or Using ODI Procedure we can call direct database queries in ODI.
How to remove the duplicate in ODI?
Use DISTINCT in IKM level. it will remove the duplicate rows while loading into target.
Suppose having unique and duplicate but i want to load unique record one table and duplicates one table?
Create two interfaces or once procedure and use two queries one for Unique values and one for duplicate values.
How to implement data validations?
Use Filters & Mapping Area AND Data Quality related to constraints use CKM Flowcontrol.
How to handle exceptions?
Exceptions In packages advanced tab and load plan exception tab we can handle exceptions.
In the package one interface got failed how to know which interface got failed if we no access to operator?
Make it mail alert or check into SNP_SESS_LOg tables for session log details.
How to implement the logic in procedures if the source side data deleted that will reflect the target side table?
User this query on Command on target Delete from Target_table where not exists (Select 'X' From Source_table Where Source_table.ID=Target_table.ID).
If the Source have total 15 records with 2 records are updated and 3 records are newly inserted at the target side we have to load the newly changed and inserted records
Use IKM Incremental Update Knowledge Module for Both Insert n Update operations.
Can we implement package in package?
Yes, we can call one package into other package.
How to load the data with one flat file and one RDBMS table using joins?
Drag and drop both File and table into source area and join as in Staging area.
If the source and target are oracle technology tell me the process to achieve this requirement(interfaces, KMS, Models)
Use LKM-SQL to SQL or LKM-SQL to Oracle , IKM Oracle Incremental update or Control append.
what we specify the in XML data server and parameters for to connect to xml file?
File name with location :F and Schema :S this two parameters
How to reverse engineer views(how to load the data from views)?
In Models Go to Reverse engineering tab and select Reverse engineering object as VIEW.
What are the types of Variables?
A variable is an object that stores a single value. This value can be a string, a number or a date. The value is stored in Oracle Data Integrator, and can be updated at run-time.
The value of a variable can be updated from the result of a query executed on a logical schema. For example, it can retrieve the current date and time from a database.
A variable can be created as a global variable or in a project. Global variables can be used in all projects, while project variables can only be used within the project in which they are defined.
Where we can use variables?
Variables can be used in all Oracle Data Integrator expressions:
What are Variable Steps?
|Declare Variable||When a variable is used in a Package (or in elements of the topology which are used in the Package), it is strongly recommended that you insert a Declare Variable step in the Package.This step explicitly declares the variable in the Package.|
|Refresh Variable||This step refreshes the variable by running the query specified in the variable definition.|
|Set Variable||There are two functions for this step:|
1. Assign sets the current value of a variable.
2. Increment increases or decreases a numeric value by the specified amount.
|Evaluate Variable:||This step compares the value of the variable with a given value according to an operator. If the condition is met, then the evaluation step is true, other-wise it is false. This step allows for branching in Packages.|
What is Work Repository ?
Each work repository is attached to a master repository, therefore, information about the physical connection to a work repository is stored in the master repository it is attached to.
Defining a connection to a work repository consists of defining a connection to a master repository, then selecting one of the work repositories attached to this master repository.
What is Master Repository ?
The Master Repository is a data structure containing information on the topology of a company's IT resources, on security and on version management of projects and data models. This repository is stored on a relational database accessible in client/server mode from the different modules.
Generally, only one master repository is necessary.
However, in exceptional circumstances, it may be necessary to create several master repositories in one of the following cases:
- Project construction over several sites not linked by a high-speed network (off-site development, for example).
- Necessity to clearly separate the interfaces' operating environments (development, test, production), including on the database containing the master repository. This may be the case if these environments are on several sites.
What is a Procedure?
A Procedure is a reusable component that allows you to group actions that do not fit in the Interface framework. (That is load a target datastore from one or more sources).
What is Model ?
An Oracle Model is a set of datastores corresponding to views and tables contained in an Oracle Schema. A model is always based on a Logical Schema. In a given Context, the Logical Schema corresponds to a Physical Schema. The Data Schema of this Physical Schema contains the Oracle model's tables and views.
What is a Package ?
The package is the biggest execution unit in Oracle Data Integrator. A package is made of a sequence of steps organized in an execution diagram.
What is User Parameters?
Oracle Data Integrator saves user parameters such as default directories, windows positions,etc. User parameters are saved in the userpref.xml file in /bin.
What is a Project?
A project is a group of objects developed using Oracle Data Integrator.
What is Folder?
Certain objects in a project are organized into folders and sub-folders.
What is an Interface?
An interface consists of a set of rules that define the loading of a Datastore or a temporary target structure from one or more source Datastores.
What is Sequence?
A sequence is an variable automatically incremented when used. Between two uses the value is persistent.
What is User Functions ?
User functions enable to define customized functions or "functions aliases", for which you will define technology-dependant implementations. They are usable in the interfaces and procedures.
What is Marker?
Elements of a project may be flagged in order to reflect the methodology or organization of the developments.
Flags are defined using the markers. These markers are organized into groups, and can be applied to most objects in a project.
What is Context?
A context is a set of resources allowing the operation or simulation of one or more data processing applications. Contexts allow the same jobs (Reverse, Data Quality Control, Package, etc) to be executed on different databases and/or schemas.
In Oracle Data Integrator, a context allows logical objects (logical agents, logical schemas) to be linked with physical objects (physical agents, physical schemas).
What is Sequences?
A sequence is a variable that increments itself each time it is used. Between two uses, the value can be stored in the repository or managed within an external RDBMS table.
Oracle Data Integrator supports two types of sequences:
- Standard sequences, whose last value is stored in the Repository.
- Specific sequences , whose last value is stored in an RDBMS table cell. Oracle Data Integrator undertakes to read the value, to lock the row (for concurrent updates) and to update the row after the last increment.
What is Session?
A session is an execution (of a scenario, an interface, a package or a procedure,...) undertaken by an execution agent. A session is made up of steps which are made up of tasks.
What is Session Tasks?
The task is the smallest execution unit. It corresponds to a procedure command in a KM, a procedure, assignment of a variable, etc