What is system log, Database Management System

Assignment Help:

What is system log?  What are the entries?      

Ans:  The system log that is generally written on stable storage contains the redundant data required to recover from volatile storage failures and as well from errors discovered by the transaction or the database system. System log is as well known as log and has sometimes been called the DBMS journal. It consists of the following entries (also known as log records):

a. [start_transaction, T]: Points out that transaction T has started execution.

b. [write_item, T, X, old_value, new_value]: Points out that transaction T has changed the value of database item X from old_value to new_value.

c. [read_item, T, X]: Points out that transaction T has read the value of database item X.

d. [commit, T]: Points out that transaction T has completed successfully, and affirms that its effect can be committed (recorded permanently) to the database.

e. [abort, T]: Points out that transaction T has been aborted.


Related Discussions:- What is system log

Control as a state machine engine, Control as a State Machine Engine F...

Control as a State Machine Engine First let us define the state machine: "the state machine is a machine which is an object but not an application object. It is a part of lang

Write the sql queries using data manipulation language, Problem 1. Writ...

Problem 1. Write the SQL queries using Data Manipulation Language (DML) statements. Insert values into student table with field names using insert command Display the

Why containment is important in oosystems, Why containment is important in ...

Why containment is important in oosystems? Containment is an significant concept in oosystems because it allows dissimilar users to view data at different granularities.

What is conceptual schema, What is conceptual schema? The schemas at th...

What is conceptual schema? The schemas at the view level are known as subschema that describe dissimilar views of the database.

Create records in a table - data structures, In this exercise you will crea...

In this exercise you will create ten records, each containing the following fields: student name, class:  Freshman, Sophomore, Junior or Senior, Major:  Liberal Arts or General Sci

Non-redundant cover and canonical cover, Given the following set of functio...

Given the following set of functional dependencies {cf?bg, g?d, cdg?f, b?de, d?c} defined on R(b,c,d,e,f,g) a.Find a non-redundant cover. b.Find a canonical cover.

Benefits of using a relational database management system, Question 1: ...

Question 1: a) What is the difference between a non-impact and impact printer? b) Which type of printer is generally used in a supermarket to print your receipt? Describe

How many types of locks are there, Depending upon the rules we have found, ...

Depending upon the rules we have found, we can classify the locks into two types. Shared Lock: A transaction might be acquiring shared lock on a data item in order to read it

What is abstraction, What is abstraction? Abstraction in the object ori...

What is abstraction? Abstraction in the object orientation is a idea that provide opportunity to express necessary properties of object without providing much details of the im

Unix System Administration, What Command You Use What Day of the week were ...

What Command You Use What Day of the week were you born

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd