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Lesson 7Testing Backup and Recovery Plan
Objective What specific way can disaster recovery plans be tested

Learn why a DBA should test the backup and recovery plan

An untested Backup and Recovery Plan is worse than no plan at all. At least with no plan you know that you will be in trouble should the system fail. An untested backup will give you a false sense of security. I would venture to say that more often than not most Oracle (and non-Oracle) sites do not practice a good, well-tested backup and recovery strategy.. Here is an example that illustrates the importance of testing your backup and recovery plan. A small company in New York called me one day. They had a corrupt database that they could not recover. After some investigation, it turned out that the system had crashed several months before. The DBA rebooted the machine, noted the outage, and continued on with his work. The system seemed to be running fine. When I arrived, I determined that the database had been corrupted in the original crash and this corruption had propagated throughout later backups. As a result, they had no clean backups. Their backup plan was perfectly good, but they had no recovery plan. It took 2 weeks to restore their database to a useable state. If you don't want this to happen at your company, test your backup and recovery plan.

How to prepeare as DBA

After countless hours of scouring the Internet, you have come across a job posting for a junior Oracle DBA position, which includes the words 0-2 years experience, meaning the position may not require any experience. With your fresh technical knowledge acquired through Oracle training and no workplace or on the job experience, what can you do to improve the probability of being hired?
Obviously, no one expects you to be the world's next Oracle Certified Master, but on the other hand, if your academic background includes several database administration courses, no one expects you have a blank stare on your face when asked to name five types of constraints on a table.
Question: What are the six kinds of constrains on a table?
Answer:Type of constraint definition:
  1. C (check constraint on a table)
  2. P (primary key)
  3. U (unique key)
  4. R (referential integrity)
  5. V (with check option, on a view)
  6. O (with read only, on a view)

Question: What is a check constraint on a table in Oracle?
A check constraint on a table in Oracle is a rule that is defined to limit the values that can be inserted or updated in a specific column of a table. Check constraints are used to enforce business rules and data integrity at the database level, ensuring that only valid data is entered into the database.
Here's an example of how a check constraint can be defined in Oracle:
CREATE TABLE employees (
   name VARCHAR2(50),
   age NUMBER,
   salary NUMBER,
   hire_date DATE,
   CONSTRAINT chk_salary CHECK (salary > 0),
   CONSTRAINT chk_age CHECK (age >= 18)

In this example, two check constraints have been defined on the employees table. The chk_salary constraint ensures that the salary column must be greater than zero, while the chk_age constraint ensures that the age column must be equal to or greater than 18.
When a user tries to insert or update a row in the employees table, Oracle checks whether the values being inserted or updated meet the conditions specified by the check constraints. If the values violate the constraints, the insert or update operation is rejected and an error is returned.
Check constraints provide an easy way to enforce data integrity rules and business rules at the database level. They can help ensure that only valid data is entered into the database, which can improve data quality and reduce the risk of errors and inconsistencies.

The Competition

Believe it or not, some companies do go out of their way to hire what can be considered less than junior DBAs. What do junior DBAs grow up to be? The answer is senior DBAs. In other words, companies need a mix of experience levels in order to grow or groom workers into more senior positions. An applicant with 10-plus years of experience applying for this position is going to raise some concerns (i.e., desperate for a job, and will bail when a better one comes along). Someone with 3-5 years experience and armed with a decent amount of experience, especially if the company knows it can get that person at a reduced salary (compared to what would otherwise be commensurate), is likely to be whom you are up against.
What you lack in experience can be countered with a demonstrable understanding of basic concepts and fundamentals. I would say it is better to have a decent mastery of core items as opposed to knowing a little bit about many things but at the price of not being able to go into detail about of any of them.

Preparation Strategies

What are some strategies available to you to increase your odds of being hired? Answering this question is fairly easy because there are published documents or material at your disposal. The source repository covers two areas:
  1. What is in the job description, and
  2. exam objectives listed in the candidate guides for Oracle's certification program.

The next lesson concludes this module.