Question

Complete the following questions with proper citations; there is a 150-word minimum per question. Questions: What is the difference between a logical backup and an image copy backup? What is a “quiesce” point, and why is it important for point-in-time recovery? Name and describe the three types of database failures that require recovery. Name and describe four factors that impact the duration of recovery.

Answer 1

1. What is the difference between a logical backup and an image copy backup?

Ans:

In logical backup technique, the IMPORT/EXPORT utilities are used to create the backup of the database. A logical backup backs-up the contents of the database. A logical backup can be used to restore the database to the last backup. A logical backup copies data, but not physical files, from one location to another. A logical backup is used to move or archive a database, tables, or schemas and to verify database structures. A logical export backup generates necessary Structured Query Language (SQL) statements to obtain all table data that is written to a binary file

Image copies are exact byte-for-byte copies of files. You can create an image copy by copying a file at the operating system level. Unlike copying files at the operating system level, however, image copies created through RMAN are recorded in the RMAN repository so that RMAN can use these copies during database restore operations and recovery.

2. What is a “quiesce” point, and why is it important for point-in-time recovery?

Ans:

A quiesce point is a point at which data is consistent across these objects.The QUIESCE utility establishes a quiesce point for a table space, partition, table space set, or list of table spaces and table space sets. You can later recover a table space to its quiesce point by using the RECOVER utility.

The RECOVER utility can recover data to a prior point-in-time with consistency without a quiesce point. The utility can recover objects with transactional consistency, which means that the objects contain only data that has been committed. However, recovering objects to a quiesce point can be faster because no work must be backed out. You might also want to establish quiesce points for related sets of objects if you need to plan for a point-in-time recovery for the entire set.

Recovering data to a prior time is a point-in-time recovery. You can recover objects to a particular RBA, LRSN, or image copy.

3. Name and describe the three types of database failures that require recovery.

Ans:

1. System Crash: A system crash usually refers to any kind of bugs or hardware malfunction in the operating system or the database software. It can bring the processing of transaction to a halt and can even cause the loss of content residing on volatile storage such as main memory, cache memory, RAM, etc.
2. Media Failure: Media failures are caused by a head crash or unreadable media. These types of data failures are considered one of the most serious because it is possible for entire data loss. Media failures usually leave database systems unavailable for several hours until recovery is complete, especially in applications with large devices and high transaction volume.
3. Application Software Errors: When the resource limit is exceeded, bad input, logical or internal errors occur, or any other factors related to the application software is compromised, transactions can fail giving way to database failure.