Showing posts with label 10g. Show all posts
Showing posts with label 10g. Show all posts

May 08, 2022

Top 20 Oracle 10g Interview Questions and Answers

 

             The Oracle Database 10g Standard Edition is designed for medium-sized businesses. Oracle's Real Application Cluster features are included to protect against hardware failures. It's simple to set up and configure, and it includes its own clustering software, storage management, and other self-managing features. Oracle Database 10g Standard Edition maintains all of your data and lets all of your business applications to benefit from Oracle Database's renowned performance, security, and reliability. It also has full upward compatibility with Oracle Database 10g Enterprise Edition, ensuring that your investment is protected as your needs change.


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Ques. 1): What are the components of an Oracle database's logical database structure?

Answer:

The following are the components of Oracle's logical database structure:

Tablespaces: Tablespaces are the logical storage units that make up a database. This tablespace is a collection of logical structures that are linked together. To be more specific, tablespace groupings are linked to logical structures.

Database Schema Objects: A schema is a set of database objects that belong to a single user. Tables, indexes, views, stored procedures, and other objects are among the objects. The user is the account in Oracle, and the schema is the object. It is also possible to have a schema without specifying a user in database platforms.


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Ques. 2): What is the connection between the database, tablespace, and data file?

Answer:

An Oracle database has one or more tablespaces, which are logical storage units. Each tablespace in an Oracle database is made up of one or more datafiles. The complete data of databases is stored in these tablespaces. When we talk about datafiles, we're talking about the physical structure that tells the operating system which Oracle software is running.


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Ques. 3): What is the difference between DB file sequential read and DB File Scattered Read ?

Answer:

DB File Scattered Read is related to index read, whereas DB File Sequential Read is related to whole table scan. DB File sequential read reads blocks into contiguous memory, whereas DB File dispersed read reads multiple blocks into buffer cache.


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Ques. 4): Which variables should be addressed when establishing a table index? How do I choose a column for indexing?

Answer:

The size of the database and the amount of data determine how an index is created. If the table is vast and only a few data points are required for selection or reporting, an index must be created. Cardinality and frequent usage in the where condition of a select query are two primary reasons for selecting columns for indexing. Because configuring main key or unique key immediately creates unique index, the business rule also forces the creation of indexes like primary keys.

It is important to note that creation of so many indexes would affect the performance of DML on table because in single transaction should need to perform on various index segments and table simultaneously.


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Ques. 5): What does Oracle's ANALYZE command do?

Answer:

This command "Analyze" is used to conduct different operations on an index, table, or cluster. The following is a list of Oracle commands that use the ANALYZE command:

The Analyze command is used to find migrated and chained table or cluster rows.

It is used to verify an object's structure.

This assists in gathering statistics about the object that the user is using, which are subsequently put in the data dictionary.

It also aids in the deletion of statistics from the data dictionary that are used by an object.


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Ques. 6): What is the DUAL table's data type?

Answer:

The Dual table is a single-column table in the Oracle database. Dummy is a single Varchar2(1) column in this table with the value 'X'.


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Ques. 7): Is it possible to create an index online?

Answer:

YES. Indexes can be created and rebuilt online. This allows you to change basic tables while also building or rebuilding indexes on those tables. DML actions are permitted while the index is being built, but DDL operations are not permitted.

When constructing or rebuilding an index online, parallel execution is not supported.

CREATE INDEX emp_name ON emp (mgr, emp1, emp2, emp3) ONLINE;


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Ques. 8): When the R/3 system is active, why is a small dump written during an offline backup?

Answer:

BRBACKUP terminates the database during an offline backup, however the present R/3 system is unaware of this. As a result, the first work process that loses its database connection creates a small dump. Until the database is available again, all work processes move into reconnect mode. As a result, because the database cannot be accessed, one (or more) brief dumps are usually produced during an offline backup.


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Ques. 9): How can you track a user's password change in Oracle?

Answer:

Oracle only keeps track of the password's expiration date based on when it was last modified. You may discover when a password was last changed by listing the view DBA USERS.EXPIRY DATE and subtracting PASSWORD LIFE TIME. The PTIME column in the USER$ database (on which the DBA USERS view is based) can also be used to check the last password change time. However, if PASSWORD REUSE TIME and/or PASSWORD REUSE MAX are configured in a profile given to a user account, you can look up the password change date in the dictionary table USER HISTORY$.

SELECT user$.NAME, user$.PASSWORD, user$.ptime, user_history$.password_date

FROM SYS.user_history$, SYS.user$

WHERE user_history$.user# = user$.user#;


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Ques. 10): What is Secure External password Store (SEPS) ?

Answer:

You can store password credentials for connecting to databases using SEPS by utilising a client-side Oracle wallet, which also stores signing credentials. This capability has been available since Oracle 10g. Thus, embedded username and passwords were no longer required in application code, scheduled jobs, or scripts. This decreases risk because passwords are no longer accessible, and password management policies can be implemented more quickly without having to alter application code whenever the login and password change.


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Ques. 11): Why do we require the CASCADE option when using the DROP USER command to drop a user, and why do "DROP USER" instructions fail when we don't use it?

Answer:

If a user has an object, you will not be able to delete that user without using the CASCADE option. The DROP USER command with the CASCADE option deletes the user and all associated items. Because this is a DDL command, rollback is not possible after it has been executed.


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Ques. 12): What is the difference between Redo, Undo, and Rollback?

Answer:

When it comes to Redo, Rollback, and Undo, I always get a little confused. They all sound pretty much the same, or at least very similar.

Every Oracle database has a collection of redo log files (two or more). The redo log keeps track of all data changes, including both uncommitted and committed ones. Oracle saves archive redo logs in addition to online redo logs. In recovery scenarios, all redo logs are used. Rollback: More specifically, section rollback. The data in rollback segments is saved as it was before any modifications were made. The redo log, on the other hand, is a record of the inserts, updates, and deletions.

Undo: Rollback segments. They both are really one in the same. Undo data is stored in the undo tablespace. Undo is helpful in building a read consistent view of data.

 

Ques. 13): Do you have more than three Linux instances running? How do you figure out which shared memory and semaphores belong to which instance?

Answer:

Oracle provides an undocumented utility called Oradebug. The oradebug help command displays a list of oracle commands.

SQL>oradebug setmypid

SQL>oradebug ipc

SQL>oradebug tracfile_name

 

Ques. 14): Why aren't all Oracle faults recorded in the Alert Log?

Answer:

In the Alert Log, Oracle only logs critical problems. The majority of Oracle error codes are not recorded (unfortunately this may also include error codes that are genuinely critical). As a result, it's common to discover faults in the Oracle application that aren't visible in the Alert Log.

 

Ques. 15): There is no room available to add datafiles to enhance temp tablespace because it is completely full. What can you do to free up TEMP tablespace in that case?

Answer:

Closing some of the database's idle sessions will help you free up some TEMP space. You can also make use of:

Alter Tablespace PCTINCREASE 1' ;

'Alter Tablespace PCTINCREASE 0;

 

Ques. 16): What is the difference between row chaning and row migration?

Answer:

Row Migration:  When an update to a row causes it to no longer fit on the block, it migrates (with all of the other data that exists there currently). A migration means that the entire row will be moved, with only the «forwarding address» remaining. As a result, the original block only has the new block's rowid and the entire row is transferred.

Row Chaining: A single database block cannot hold more than one row. For example, if your database uses a 4KB blocksize and you need to insert an 8KB row, Oracle will use three blocks and save the information in pieces. Row chaining can occur under the following circumstances: Tables with a rowsize greater than the blocksize. Chained rows are common in tables containing LONG and LONG RAW columns. Oracle breaks broad tables split into sections, therefore tables with more than 255 columns will have chained rows. Rather of having a forwarding address on one block and data on another, we now have data on two or more blocks.

 

Ques. 17): How can I erase a data file that I accidentally created?

Answer:

In most circumstances, you can use RESIZE or RENAME to fix a data file that was generated with the improper size or in the wrong location. You have the following alternatives if you want to drop the data file again:

A produced data file can only be erased during a tablespace reorganization up to and including Oracle 9i. There are no other viable alternatives.

As of Oracle 10g, an empty data file can also be dropped with the following command:

ALTER TABLESPACE DROP DATAFILE ' ';

If there are still extents in the data file, this command fails with ORA-03262. In this case, the affected segments must first be relocated so that the extents are released.

 

Ques. 18): What is the ideal file size for data files?

Answer:

It is impossible to provide a straightforward solution to this topic. In most cases, the size of the data files has no bearing on database activity. However, keep the following considerations in mind:

Make sure the Oracle parameter DB FILES is set high enough. Otherwise, once this limit is reached, new data files cannot be produced.

The fewer the datafiles, the faster they can be restored individually during a backup.

BEGIN BACKUP processes in online backups are likely to take longer the smaller the data files are, and hence the more data files there are.

Data files that are too large aggravate performance problems that are caused by inode locking, since parallel processes may become serialized on the data file inode.

On occasion, size restrictions may prevent the system from using data files that exceed a certain size (often 2GB).

 

Ques. 19): Why does the order of the online redo logs occasionally change?

Answer:

This redo log becomes the next redo log if the next online redo log is still archived and another redo log is available for overwriting. The order of the online redo logs is now altered. Because the alternative would be an archiver stuck, at least briefly, this behaviour is preferable.

Only if many archive processes run in parallel and do not run again when the redo logs are archived may this situation arise. To avoid this issue, see if the archiver's performance (I/O tuning) can be improved. You must also avoid getting an archiver stuck due to a fully operational archive file system.

This problem cannot occur if the number of archiver processes is limited to one by LOG_ARCHIVE_MAX_PROCESSES

 

 

Ques. 20): On my system, why do Oracle processes run as the sid>adm user?

Answer:

By default, the UNIX PS command displays the true user, not the actual user. As a result, having adm as the displayed user for Oracle processes is not a problem. The only thing that matters is that the Oracle executable has the appropriate permissions.  

 

 

November 19, 2021

Top 20 Oracle ADF Interview Questions and Answers

 

Ques: 1). What is Oracle ADF, and how does it work?

Answer: 

The Oracle Application Development Framework (Oracle ADF) is an end-to-end application framework that simplifies and accelerates the implementation of service-oriented applications by leveraging J2EE standards and open-source technologies. Oracle ADF can help you construct enterprise applications that use web, wireless, desktop, or web services interfaces to search, display, generate, change, and validate data. With drag-and-drop data binding, visual UI design, and team development tools built-in, Oracle JDeveloper 10g and Oracle ADF provide an environment that covers the whole development lifecycle from design to deployment.


Oracle Fusion Applications interview Questions and Answers


Ques: 2). What is Managed Bean, and how does it work?

Answer: 

Managed beans are JavaBean objects that are managed by a JSF implementation. A managed bean represents the process of creating and managing a bean. It has nothing to do with the functionality of the bean.

A managed bean is one that is produced and initialised in a controlled manner. JSF, as you may know, employs a lazy initialization model. It means that the bean in a specific scope is created and initialised on-demand, that is, when the bean is requested for the first time.


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Ques: 3). What exactly is task flow?

Answer: 

ADF task flows are a modular way to defining application control flow. You can break up an application into reusable task flows rather than portraying it as a single huge JSF page flow. A piece of the application's navigational graph is contained in each task flow. The activities are the nodes in the task flows. A simple logical process, such as displaying a page, running application logic, or calling another task flow, is represented by an activity node. Control flow cases are the interactions between the activities.


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Ques: 4). What are the benefits of task flow over JSF flow?

Answer: 

  • ADF task flows have a number of advantages over JSF page flows.
  • The app can be divided into a set of modular processes that communicate with one another.
  • Views, method calls, and calls to other task flows can all be added to the task flow diagram.
  • Navigation is used to move between sites and other operations, such as routers.
  • Task flows created using ADF can be reused inside the same or a different application. You might decide to reuse task flows after you've broken up your application into task flows.
  • Data can be transmitted between activities inside the task flow using shared memory scope (for example, page flow scope).
  • Page flow scope defines a unique storage area for each instance of an ADF bounded task flow.


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Ques: 5). What is Adf Event handling and how does it work?

Answer: 

Event handling is normally done on the server in classic JSF applications. JSF event handling is based on the JavaBeans event paradigm, in which the JSF application uses event classes and event listener interfaces to handle events provided by components.

Clicking a button or link, selecting an item from a menu or list, and altering a value in an input field are all examples of user events in an application. When a user activity, such as pressing a button, occurs, the component creates an event object, which holds information about the event and identifies the component that caused it. An event queue is also created for the event. JSF instructs the component to broadcast the event to the relevant registered listener at the appropriate point in the JSF lifecycle, which then calls the listener method to process the event. The listener method can either update the user interface or call backend application logic.

ADF Faces command components, like regular JSF components, send out ActionEvent events when they're triggered, while ADF Faces input and select components send out ValueChangeEvent events when their local values change.


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Ques: 6). What is Association Accessor?

Answer: 

It's a method for an entity instance at one end of an association to communicate with the linked entity object instance at the other end. A source assessor travels from the destination to the source, while a destination assessor travels from the source to the destination.

It is described in the entity object definition xml files, which can be used to specify cross entity relationships by view object and view link definition. Its return type is either the associated entity object definition's entity object class or 'EntityImpl' if the associated entity object definition does not have an entity object class.


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Ques: 7). What is the difference between Datacontrol.dcx and Databindings.cpx?

Answer: 

The Oracle ADF binding context for your entire application is contained in the DataBindings.cpx file, which also contains the metadata from which the Oracle ADF binding objects are constructed at runtime. When you register data controls on business services, the DataControls.dcx file is created. Oracle ADF Business Components does not generate this file. It specifies the Oracle ADF model layer data control classes (factory classes) that help the client and the accessible business service interact.


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Ques: 8). Why did you choose ADF?

Answer: 

I had already developed a strong interest in technology with the goal of making a substantial impact. As the main development framework, ADF may be used to create virtually any form of enterprise application. I became interested in this technology since it is so beneficial. Of course, this is in keeping with my goals and ambitions.

Second, ADF is widely recognised as the most advanced J2EE development framework. As a result, the ADF 11g is used to build the Oracle Fusion Middleware stack. This is why we have so many options here.

Finally, ADF contains a number of built-in components that help us with the work of developing code. This way, I can actually focus on the features of the application and how it can do more good to the business.


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Ques: 9). What is the difference between a binding context and a binding container?

Answer: 

The binding context, which is used to access the binding layer, is a runtime map between data controls and page definitions of pages in the application. The EL expression on your jspx pages gives you access to it. The page bindings are instantiated using the binding container, which is a request-scoped map. The EL expressions provide access to this. It is also accessible throughout every page request because it is a request-scoped map.


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Ques: 10). What is the difference between Visible and Render property?

Answer: 

The visible property is set to true or false depending on whether the field should be visible on the page at run time. Even though the field or component is hidden, it still exists on the page.

The render attribute is used to load the component conditionally based on a set of criteria.


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Ques: 11).  In Adf, how do you define pagination?

Answer: 

In ADF, we establish custom pagination by utilising the af:iterator tag to create a custom table as a taskflow. This renders the data collection in the same way that a table does. Now, using the ADF bindings declaration, we tie the value property of the iterator to the collection model and set the number of visible rows to 15, for example.


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Ques: 12).  What is the Adf Lifecycle and how does it work?

Answer: 

The ADF Lifecycle is divided into nine stages:

1.      Set the Context: The lifecycle, the binding container, and other values are all set.

2.      Create the Model: The application model is created by providing it with the necessary parameters. ADF is also provided the necessary instructions.

3.      Apply Input Values: This phase handles the application's access request.

4.      Validate Input Values: Verifies the values specified in phase 3 of the request.

5.      Update Model: Data is stacked up and updated when the input values have been validated.

6.      Validate Model Updates: Validate the updated input values.

7.      Process Component Updates: This is where all activities involving input values are handled.

8.      Metadata Commit: Commits the metadata runtime to the model.

9.      Prepare Render: All the activities and the final page is sent to render.

 

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Ques: 13).  What is the difference between Valuators and Converters?

Answer: 

To give conversion and validation capabilities to the ADF input components, Valuators and Convertors are used.

After the values on ADF forms are changed and submitted, converters convert the values to the type that the application accepts.

Valuators are used to enforce input component validations.

 

Ques: 14). What is Partial Page Rendering, and how does it work?

Answer: 

PPR (Partial Page Rendering) is quite similar to Ajax. PPR is a dynamic system that takes appropriate action as needed. It triggers the page when it needs to be triggered. It updates the page when it needs to. Once all of the activities are in order, PPR submits the page.

You'll need to do the following to allow partial page rendering:

Auto-submit: When auto-submit is on or set to true, the page automatically submits the values updated or changed on the page.

PartialSubmit: When the partialSubmit is set to true, the changes and updates on the page submit the page partially.

Partial trigger: When the partial trigger is on, the page renders are simply listed. Once the triggers are settled, final changes are considered.

 

Ques: 15).   Is ADF a better framework than JSF?

Answer: 

The ADF framework is based on the JSF. When it comes to processing any business application, ADF is quite smooth.

Let's look at it from the user's perspective:

The ADF possesses the following:

  • The UI is simple and straightforward to use.
  • Even if they are viewing it for the first time, anyone can readily access it.
  • Almost everything is in one location.
  • The appearance and feel are smooth and solid.
  • From the developer's perspective:
  • It's a simple platform on which to build an application.
  • More than a hundred components that are ready to use
  • Components that can be edited to alter the functionality
  • Simple to keep up with
  • Simple to set up
  • Simple to use
  • Drag and drop functionality is available.

As ADF is built on JSF, any time ADF will give you a nicer and smoother performance. JSF is, nonetheless, a very good platform too. But when it comes to comparison, ADF is better.

 

Ques: 16). What is the Role Of View Object, Entity Object, and Application Module?

Answer: 

View object: View objects show the modifications made by the user to Taskflows projects. VO aids the system in sorting through the user's actions. And it organises, filters, and maintains the task so that SQL queries may quickly discover the results when they're looking for them.

Entity object: In a database, an entity object is a row. EO is the ADF, similar to EJB in J2EE. The values in the row are also easy to recognise with EO. It encapsulated the entire row in a specific value. As a result, searching for any value in the row becomes much easier. Even two EOs might be related to one another and grouped together based on their relationship. Entity Associations are a group of connected EOs.

An application module allows a customer to access their work via the platform. AM contains all of the essential and top-level processes, as well as the most up-to-date information. AM is sometimes referred to as the transactional module because it lets clients to access their own work. In the View link form, there are also numerous VO and Entity Associates.

 

Ques: 17). What does it mean to be a Phase Listener?

Answer: 

The Oracle ADF lifecycle is fully integrated with the JavaServer Faces request lifecycle, including everything needed to set up the binding context, prepare the binding container, validate and update the ADF model, persist MDS changes, and prepare the response.

An ADF Phase Listener can be used by developers that need to listen to and engage with the request cycle. The ADF Phase Listener, unlike the Phase Listener defined in the faces-config.xml file, allows you to listen to both the standard and ADF phases. Of course, the ADF Phase Listener is written in Java and configured in the adf-settings.xml file you must generate.

The ADF PagePhaseListener can be used in any situation.

Developers can utilise either a conventional JSF listener or a particular ADF listener in the Oracle ADF framework, which provides extra ADF-specific page cycle enhancements. The ADF Lifcycle can be customised with listeners.

 

Ques: 18). What is inter-portlet communication, and how does it work?

Answer: 

When an action in one portlet causes a reaction in another, this is known as inter-portlet communication. It serves as a link between two portlets. One portlet, for example, has a checkbox with a list of products. When I select a product from the list and press the submit button, the other portlet displays the product's data.

 

Ques: 19). What is the meaning of Association Accessor?

Answer: 

It's a method for an entity instance at one end of an association to communicate with the linked entity object instance at the other end. A source assessor travels from the destination to the source, while a destination assessor travels from the source to the destination.

It is described in the entity object definition xml files, which can be used to specify cross entity relationships by view object and view link definition. Its return type is either the associated entity object definition's entity object class or 'EntityImpl' if the associated entity object definition does not have an entity object class.

 

Ques: 20). What are the various Bean Scopesin JSF types?

Answer: 

Three Bean Scopes are supported by JSF.

Request Scope: The request scope is only valid for a certain time. It begins with the submission of an HTTP request and finishes with the delivery of the response to the client.

Session Scope: From the time a session is formed until it is terminated, the session scope persists.

Application Scope: The application scope remains constant throughout the web application's lifecycle. The scope of all requests and sessions is the same.