Oracle Technical Questions
This is the part you have all been waiting on. Please if you have just skipped to this section, go back to the personal section and read it. There is much to be gained by the personal section and conveying to your interviewer who you are and how you tick from day to day. Also, the answers I am giving here are off the cuff and are not intended to be the definitive answer to these questions. There are many aspects to these questions that just cannot be answered here and honestly, you will not have time to explain any of these questions fully in the interview process. It is up to you to make sure your interviewer understands that you understand the question and have given enough information that they know you understand the concept.
**1. **Explain the difference between a hot backup and a cold backup and the benefits associated with each.
A hot backup is basically taking a backup of the database while it is still up and running and it must be in archive log mode. A cold backup is taking a backup of the database while it is shut down and does not require being in archive log mode. The benefit of taking a hot backup is that the database is still available for use while the backup is occurring and you can recover the database to any point in time. The benefit of taking a cold backup is that it is typically easier to administer the backup and recovery process. In addition, since you are taking cold backups the database does not require being in archive log mode and thus there will be a slight performance gain as the database is not cutting archive logs to disk.
**2. **You have just had to restore from backup and do not have any control files. How would you go about bringing up this database?
I would create a text based backup control file, stipulating where on disk all the data files where and then issue the recover command with the using backup control file clause.
**3. **How do you switch from an init.ora file to a spfile?
Issue the create spfile from pfile command.
**4. **Explain the difference between a data block, an extent and a segment.
A data block is the smallest unit of logical storage for a database object. As objects grow they take chunks of additional storage that are composed of contiguous data blocks. These groupings of contiguous data blocks are called extents. All the extents that an object takes when grouped together are considered the segment of the database object.
**5. **Give two examples of how you might determine the structure of the table DEPT.
Use the describe command or use the dbms_metadata.get_ddl package.
**6. **Where would you look for errors from the database engine?
In the alert log.
**7. **Compare and contrast TRUNCATE and DELETE for a table.
Both the truncate and delete command have the desired outcome of getting rid of all the rows in a table. The difference between the two is that the truncate command is a DDL operation and just moves the high water mark and produces a now rollback. The delete command, on the other hand, is a DML operation, which will produce a rollback and thus take longer to complete.
**8. **Give the reasoning behind using an index.
Faster access to data blocks in a table.
**9. **Give the two types of tables involved in producing a star schema and the type of data they hold.
Fact tables and dimension tables. A fact table contains measurements while dimension tables will contain data that will help describe the fact tables.
**10. **. What type of index should you use on a fact table?
A Bitmap index.