Technical Things To Know

1. In Oracle what is the difference between a Hot backup and  cold backup?

A cold backup is performed when there is no user activities going on within the system it is also known as offline backup. This type of backup is taken when the database is not running and no users are logged in. All the files of the database are copied and no changes during the copy are made.

A hot backup is performed when the database needs to run all the time due to critical nature of business. It is also known as online backup. All the files of the database are copied and there may be changes to the database during the copy is being carried out.

The benefit of taking a hot backup is that the database is available for use while the backup is occurring and one 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. For 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> What is Cron Jobs?

Cron jobs are time based commands which are often used to trigger shell scripts to perform actions at a particular time, similar to scheduled tasks in windows.

Typical format of Corn:

Minute(0-59) Hour(0-24) Day_of_month(1-31) Month(1-12) Day_of_week(0-6) CommandToExecute

As shown in the above picture, asterisks refers the specific blocks of time.

To display the contents of the crontab file of the currently logged in user :

$ crontab -l

To edit the current user cron jobs :

$ crontab -e

To export the cron jobs to a file:

crontab – l >> filename 

* If the filename is not specified (crontab –l)  the list of files will be displayed on the standard output (e.g. on the screen).

To import the cron jobs from a file:

crontab <filename>

* The crontab can also be modified on screen but it is easy to modify the cron jobs in file format.

2. Difference between Cold and Warm booting?

The primary difference between cold and warm booting is that, the cold booting is the process of starting up the computer that is turned off, while warm booting is the process of restarting the computer without interrupting power.

It is also called rebooting, start-up, boot up or booting. In booting, the startup instructions are loaded from the computer’s ROM (Read Only Memory) and then the operating system is loaded from the current boot disk. Primarily, the boot disk can be an internal hard drive. After loading the operating system, the boot process is completed and the computer is ready to use. Cold and warm booting are two types of booting.