Which are the drawbacks of shadow paging technique?

Disadvantages :

• Due to location change on disk due to update database it is quite difficult to keep related pages in database closer on disk.
• During commit operation, changed blocks are going to be pointed by shadow page table which have to be returned to collection of free blocks otherwise they become accessible.

What are the advantages of shadow paging?

Advantages of Shadow Paging in DBMS

• The Shadow Paging focuses on Over log-based technique.
• Overhead in Log File is eliminated.
• System recovery can be made faster from this technique as well as there is no need for Undo or Redo options.

Which are the drawbacks of the shadow page technique Mcq?

The drawback of shadow paging technique are

• All of these.
• Garbage collection.
• Data fragmentation.
• Commit overhead.

What are the common database failures?

Hardware failures may include memory errors, disk crashes, bad disk sectors, and disk full of errors among others. Hardware failures can also be attributed to design errors, inadequate or poor quality control during fabrication, overloading (use of under-capacity components) and wear out of mechanical parts.

How shadow paging scheme works in DBMS?

This is the method where all the transactions are executed in the primary memory or the shadow copy of database. Once all the transactions completely executed, it will be updated to the database. Hence, if there is any failure in the middle of transaction, it will not be reflected in the database.

What is shadow paging advantages and disadvantages?

Shadow paging is an alternative to log-based recovery techniques, which has both advantages and disadvantages. It may require fewer disk accesses, but it is hard to extend paging to allow multiple concurrent transactions. The paging is very similar to paging schemes used by the operating system for memory management.

What is VSS used for?

The Volume Shadow Copy Service (VSS), which was introduced in Windows Server® 2003, facilitates the conversation between these components to allow them to work better together. When all the components support VSS, you can use them to back up your application data without taking the applications offline.

What causes database failure?

A database failure can be defined as inability of the system to provide required functionality correctly. Database failure can be resulted due to a variety of reasons such as disk-crash, power failure, software error or even sabotage.

How is shadow paging used in a transaction?

The key idea behind the shadow-paging technique is to maintain two page tables during the life of a transaction: the current page table and the shadow page table. When the transaction starts, both page tables are identical. The shadow page table is.

How many blocks are needed for shadow paging?

The commit of a single transaction using shadow paging requires multiple blocks to be output—the actual data blocks, the current page table, and the disk address of the current page table. Log-based schemes need to output only the log records, which, for typical small transactions, fit within one block.

When do you use the shadow page table?

Another table i.e., Shadow page table is used when the transaction starts which is copying current page table. After this, shadow page table gets saved on disk and current page table is going to be used for transaction.

What happens when a shadow page is modified?

• Since the shadow page has no references (from other pages on disk), it can be modified liberally, without concern for consistency constraints, etc. When the page is ready to become durable, all pages that referred to the original are updated to refer to the new replacement page instead.