Persistent data. Transient data

Persistent data. Transient data


Contents


1. What types of data can a database contain, which is managed by DBMS?

Any database managed by the DBMS contains two types of data:

  • persistent data;
  • transient data.

2. What are permanent data?

Permanent data are a database data that is constant with respect to other, more variable, data. The word “permanent” does not mean that permanent data is immutable. Permanent data is also subject to change. This is the data that directly represents the information in the database that concerns the essence or purpose of this database. In fact, a database is a collection of persistent data that is used by the application systems of a certain organization, enterprise, etc.

To remove permanent data from the database, you need to perform a special request from the user or the database administrator.

Transient or temporary data can be deleted:

  • without applying a special request;
  • as a result of some side action of executing a DBMS or application system.

3. What data in the database do not apply to permanent data? The concept of transient data

Since the database management organization is engaged in a DBMS or some application system, besides permanent (persistent) ones, additional (non-permanent, transient) data can be used in the database. These data are also called temporary (transient) data. They are required by the DBMS to ensure proper database management.

For transient data include:

  • intermediate results;
  • input and output data;
  • control operators;
  • work queues;
  • control units;
  • other temporary data.


4. An example showing permanent data

Let a database containing information about books in a bookstore be given.

Any book is described by a table called Books, which has the following structure:

Number

Field name

Type

Explanation

1

Title

Text, 255 characters

Title of the book

2

Author

Text, 255 characters

The name of the author of the book

3

Price

Float, 2 decimal places

Cost of the book

4

Code

Text, 30 characters

Book code in the library

5

Year

Integer

Year of issue

The following table shows direct information about the books that are placed in the bookstore. The data that was entered in the table are permanent (persistent) data.

Title

Author Price Code

Year

Foundation for Object Relational Databases Christopher J. Date

195.55

342345A

1998

Relational Database Writing Christopher J. Date

205.99

342345B

1994
A Guide to the SQL Standard Christopher J. Date

187.00

342345C 1997
A Guide to DB2 Christopher J. Date

113.55

342345D 1993
A Guide to Sybase and SQL Server Christopher J. Date

256.25

342345E 1992

All other user generated data are temporary. These can be query results, recorded SQL control statements, etc.


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