IT Job Interview » DBA

DBA and Developer Questions for Oracle Views

admin — Thu, 06 May 2010 00:48:27 +0000

When hiring Oracle DBAs and developers, a lot of questions are asked about Oracle view. Although view is only one of Oracle objects and it is not that significant in my opinion, for some reason managers and business users love views, therefore in interview they usually like to ask more questions on Oracle views. The following are some of questions and answers for you to prepare:

1. What is a view and how to create one?

A view is simply the representation of a SQL statement that is stored in memory so that it can easily be re-used. For example, if you frequently use a query SELECT empid FROM emp, you may create a view as
CREATE VIEW view_emp
AS
SELECT empid FROM emp;

Then every time you query this view, Oracle will go out and execute the SQL behind the view to query the database data.

2. Can Oracle view improve performance? Why or why not?

In most cases view does improve performance because of commonality of code being used. Since a view is based on one common set of SQL, when it is called it’s less likely to require parsing. This is because the basic underlying SQL that is called is always the same. A query without parsing is faster. However, since you can add additional where clauses when calling a view, you still need to use bind variables. Additional where clauses without a bind variable can still cause a hard parse.

3. Explain how you may use view to enhance security and what are view’s limitations for security practice?

It is a two-question in one but people often miss the second one. In any database, view’s limitation for security is the issue of scalability.

Answer:

Views are commonly used to hide the tables that actually contain the data you are querying. Also, views can be used to restrict the columns that a given user has access to. Using views for security on less complex databases is probably not a bad thing. As databases become more complex, this solution becomes harder to scale and other solutions will be needed.

4. In what situation Oracle views can affect performance, and what is Oracle’s solution to this issue?

When you create complex views with many table joins to represent large subsets of query and allow many developers and end users to access these views, you may experience poor performance. In this case, you may consider Oracle’s materialized view.

5. What is materialized view and where is it used?

A materialized view is a snapshot of data that can be refreshed based on a schedule. It is a replica of a target master from a single point in time. Oracle uses materialized views to replicate data to non-master sites in a replication environment and to cache expensive queries in a data warehouse environment.

6. Can view be indexed in Oracle?

Don’t think Oracle can do everything and quickly answer ‘yes’. SQL Server offers view index, but Oracle does not do it.

Answer:

Regular Oracle view cannot be indexed, but you can utilize table level indexed to tune underlying query that generates the view.

7. Can you insert and update records in a view?

This question asks if you can execute insert or update statement directly on a view instead of on a table.

Answer:

You can only perform data manipulation language (DML) operations with simple views. Complex views don’t support DML. view is mainly used for presenting and data and simplifying query. Data insert and update should be done on table level.

8. What’s the different between GRANT CREATE VIEW and CREATE ANY VIEW?

It is not a question about view. This question checks your knowledge of controlling user privileges in Oracle database. Grant Create view gives user’s right to create new views in grantee’s schema only. GRANT CREATE ANY VIEW allow users to create views in any schema.

What is your database administration experience in configuring Oracle or other RDBMS for OLAP and decision support system?

admin — Fri, 15 Jan 2010 19:10:03 +0000

Be careful about this question. What the interviewers want to know it your knowledge and experience on OLAP DSS, but many candidates missed this point, they explained their DBA experience in general, but failed to answer what is asked. To answer this question correctly, you should provide your knowledge about the characters of OLAP and DSS systems, and how you configure the database to meet the requirements.

“I have extensive DBA experience in configuring database server for both OLTP and OLAP systems. I worked on many transaction-oriented database, I also had the opportunity to setup database for decision support systems. Nowadays most of the RDBMS provide options to setup OLAP for you during installation, you simply select this option and the installation process will configure your database suitable for OLAP and DDS applications. Of course I can always change my database configuration manually when necessary. The major difference of OLAP comparing to transaction database is that OLAP requires fast data retrieval and concurrent access. Many DSS applications run very complicated queries. In general, there are every few data manipulation activities such as insert, update, and delete. Therefore in OLAP configuration I use indexes heavily to speed up data query process. Oracle’s bitmap index and materialized views are also helpful. I would also configure table partitions based on the analysis of data structure. I would design tablespaces on different data files put on different hard disks and build tables across. That would increase concurrent access and reduce I/O bottleneck. For DSS system, I may consider de-normalize the data structure and build dement ional database for reporting and BI purpose. Depending on the specific project, I may implement other options such as configuring the database cache to meet the OLAP and DSS needs.”

What Makes a Top Flight Oracle DBA? How to Obtain the Skills and Experience You Need to Become a High-Paid Oracle Database Admin

admin — Tue, 18 Aug 2009 17:02:25 +0000

Look at the business facts:

Database is the heart of today’s enterprise.

The whole IT business works around databases.

Oracle is the leading enterprise database server.

That makes an Oracle Database Administrator (DBA) so special. As you can see, Oracle DBAs play critical roles in IT, no doubt that experienced DBAs are in high demand and get paid well.

What Are Oracle DBAs Doing at Work
Oracle DBAs are responsible for the development, design, implementation and maintenance of one or multiple Oracle database servers. These database servers support mission critical business applications in client-server structure or web-based architecture. These applications could be built in Microsoft .Net framework or J2EE platform. Some applications might be extremely complex. Oracle databases also support data mart, data warehouse, and business intelligence systems.

Oracle DBA’s daily administration work includes database server monitoring, performance tuning, and database backup and recovery. From time to time, Oracle DBAs are required for installation, upgrade, configurations of Oracle database software, and creating new database instances.

In most organizations, database design is a big part of DBA’s task. Oracle DBAs are good at designing logical database model by creating entity relationship diagram (ERD) using case design tools such as Oracle Designer and Sybase PowerDesigner. Oracle DBAs must be able to design the physical data models with schema, roles, tablespaces, tables, views, and other database objects.

Technical Environment

As an Oracle DBA, you may work in the development environment, production environment, or both.

In a heavy development environment, you must provide the expertise in guiding the developers in database platform and design, recommending database design alternatives and participate in design reviews. There will also be customer and end user interaction to ensure their needs are being met from the database side as well. You must be able to identify data needs, such as access, protection, quality and maintenance requirements. DBAs in development environment may be required to code stored procedures and packages to implement business rules.

In the production environment, your task is focused on availability, performance, and security. Your job could be making the database available 7/24 by implementing advanced Oracle technologies such as parallel server and standby database. You may need to tune the database constantly to optimize the transaction processes. You must have a solid backup/recovery plan and you always have to deal with the security processes and procedures to make sure your data is safe.

Skills for Top Flight DBAs

Top-level Oracle DBAs demonstrate the following expert knowledge and skills:

1. Relational database management system (RDBMS) concepts, design, and deployment.

2. Designing, developing, and supporting large RDBMS in the Oracle 8i or 9i environments.

3. Mastering Oracle database software for installation, upgrading, and configuration.

4. Installing and managing Oracle Parallel Server (OPS).

5. Concepts and practices on logical and physical database design.

6. Skills for database performance tuning – including server tuning and application tuning.

7. Developing and implementing backup and recovery plans.

8. Writing SQL query scripts and operating system level scripts to monitor database and perform DBA tasks.

9. Writing PL/SQL stored procedures and packages to implement business logic.

10. Using case tools for data modeling, analyzing business rules and creating entity relationship diagram.

11. Using Oracle Enterprise Manager to perform DBA tasks.

12. Using Oracle RMAN to perform backup/recovery tasks.

13. Data Warehouse and data mart physical structures and design.

14. Using ETL (Extraction, Transformation and Loading) tools such as PowerMart / Informatica.

15. Some knowledge and working experience on other databases such as IBM DB2 and Microsoft SQL Server.

16. Fundamental knowledge of operating systems (UNIX, Windows, etc) and networking (TCP/IP, Novel, Internet, etc.)

17. Knowledge on specific industry – banking, financial, insurance, retail, etc.

How to Obtain Oracle DBA Skills and Experience

There are two kinds of skills in IT – intelligence based skills and experience-based skills. Programming skills, for instance, are intelligence-based skills that count on your brain cells. On the other hand, DBA skills are more likely experience based. DBA skills are obtained from the actual work.

If you are in a database related position, you can take advantage of the environment and build these skills that I listed above. If you have a IT job but it is not directly related to database tasks on the server side, you may talk to the DBA to give you certain level of access to the database so you can play with it. Most programmers and developers have enough database privileges that they can use to work and play in order to gain database server experience.

Even if you don’t have access to Oracle database at work, or don’t work on an IT job at all, you can still get hands-on skills and experience with Oracle database and market your self as a experienced Oracle DBA for job switching or re-joining the workforce. All you need is to build an Oracle database environment on your PC, and then, work, play, create, break, do whatever you like on it. That’s how you get the hands-on experience.

You can download the fully functional Oracle database software for trail/testing purpose from Oracle website. Oracle database is available in different editions – Personal, Standard, and Enterprise. You may start with the Personal Edition that is smaller. If you want to explore more advanced Oracle technologies, use the Enterprise Edition. Oracle database software can be installed on WindowsNT/2000/XP and Linux. If your PC is running on Windows 2000 Professional, XP, or Linux, you’ll be able to put Oracle database on it.

You need to become a member of Oracle Technology Network in order to download Oracle software. The membership is free. You just need to go to http://otn.oracle.com/ to sign up. After you create you account with user/password, you can go to http://otn.oracle.com/software/content.html to download Oracle database software.

Oracle database software comes with full set documentations in HTML and PDF format. By following the instructions in the documentation, you should have no problem to install the software, create a database instance, and start to play with it. Oracle Technology Network provides a lot of useful information to help you obtain skills and build experience in Oracle database.

Since Oracle is such a popular database, there are tons of technical books and free resources online that you can use. The following link provides online resources on database related topics.
Online Resources for Database

Education and Certifications

Most Oracle DBAs hold a Bachelor’s Degree at least. A major in Computer Science or IT related field is preferred. However Oracle DBAs come from very diversified academic background. I’ve met top level DBAs who were educated in Chemistry, Mining Engineering, Political Science, Linguistics, etc. In IT industry, experience is more countable. If you work to build your experience, you can become a successful Oracle DBA.

Oracle DBA certification is one of the highly valued credentials in IT industry. If you plan to work your way to become a top flight Oracle DBA, certification is strongly recommended. You can find detailed information about Oracle DBA certification at Oracle’s website by clicking http://www.oracle.com/education/certification/.

Database Administrator Job Description

admin — Thu, 02 Nov 2006 00:17:58 +0000

A database administrator (DBA) is responsible for the planning, maintenance and development of a database. The database approach incorporates the following principles:

data remains consistent across the database;
data is clearly defined;
users access data concurrently, in a form that suits their needs;
there is provision for data security and recovery control (all data is retrievable in an emergency).

For example, an estate agent may be able to view details of properties/clients and branch contact details. However, making local amendments to details and viewing sensitive data on fellow employees will depend on access permissions and privileges.
Typical work activities

The work of a database administrator (DBA) will vary according to the nature of the employing organisation and the level of responsibility associated with the post. Some of the work may involve specialising in database development or pure maintenance.

Typical responsibilities could include some or all of the following:

establishing the needs of users;
planning dataflows for a new or revised database;
mapping out the ‘conceptual design’ for a planned database in outline;
considering both ‘back end’ organisation of data and ‘front end’ accessibility for end users;
refining the ‘logical design’ so that it can be translated into a specific data model;
further refining the ‘physical design’ to meet system storage requirements;
testing new systems;
maintaining data standards, including adherence to the Data Protection Act;
writing database documentation, including data standards, procedures and definitions for the data dictionary (‘metadata’);
controlling access permissions and privileges;
training users;
meeting users’ access requirements and resolving their problems;
ensuring that storage, archiving, backup and recovery procedures are functioning correctly;
capacity planning;
working closely with IT project managers, database programmers and web developers;
providing technical support for outdated ‘legacy’ systems;
communicating regularly with technical, applications, and operational staff, to ensure the database integrity and security;
commissioning and installing new applications.

Because of the increasing levels of hacking and sensitive nature of data stored, security has become an increasingly important aspect of the work.

What Makes a Top Flight Oracle DBA?

admin — Sun, 16 Jul 2006 22:53:44 +0000

How to Obtain the Skills and Experience You Need to Become a High-Paid Oracle Database Administrator.

Look at the business facts:

Database is the heart of today’s enterprise.

The whole IT business works around databases.

Oracle is the leading enterprise database server.

That makes an Oracle Database Administrator (DBA) so special. As you can see, Oracle DBAs play critical roles in IT, no doubt that experienced DBAs are in high demand and get paid well.

Technical Environment

As an Oracle DBA, you may work in the development environment, production environment, or both.

Skills for Top Flight DBAs

Top-level Oracle DBAs demonstrate the following expert knowledge and skills:

1. Relational database management system (RDBMS) concepts, design, and deployment.

2. Designing, developing, and supporting large RDBMS in the Oracle 8i or 9i environments.

3. Mastering Oracle database software for installation, upgrading, and configuration.

4. Installing and managing Oracle Parallel Server (OPS).

5. Concepts and practices on logical and physical database design.

6. Skills for database performance tuning – including server tuning and application tuning.

7. Developing and implementing backup and recovery plans.

8. Writing SQL query scripts and operating system level scripts to monitor database and perform DBA tasks.

9. Writing PL/SQL stored procedures and packages to implement business logic.

10. Using case tools for data modeling, analyzing business rules and creating entity relationship diagram.

11. Using Oracle Enterprise Manager to perform DBA tasks.

12. Using Oracle RMAN to perform backup/recovery tasks.

13. Data Warehouse and data mart physical structures and design.

14. Using ETL (Extraction, Transformation and Loading) tools such as PowerMart / Informatica.

15. Some knowledge and working experience on other databases such as IBM DB2 and Microsoft SQL Server.

16. Fundamental knowledge of operating systems (UNIX, Windows, etc) and networking (TCP/IP, Novel, Internet, etc.)

17. Knowledge on specific industry – banking, financial, insurance, retail, etc.