Importance of Concurrent scheduling in database

To reduce transaction waiting time and improve throughput we use concurrent scheduling in database. Concurrent means two or more transaction run at a time concurrently. There are two reasons for allowing concurrent scheduling.
(a) Improved throughput and resource utilization: 
We can divide a transaction into many subprogram. Some program related to I/O activity and some are related to CPU activity. When a transaction runs without concurrency, it takes full time to execute and at that time other transaction need to wait to run. But when a transaction run concurrently, some program run in the processor and some run in disks. So the waiting time of other program also decrease and the throughput also increase. Correspondingly the processor and disk utilization also increase. So we can say that concurrent execution improved throughput and resource utilization.
(b) Reduced waiting time:
Concurrent execution reduces the unpredictable delays in running transaction. In the database system there are many transactions running, some are short and some are long. If transactions run serially, a short transaction may have to wait for a preceding long transaction to complete, which can lead to unpredictable delays in running a transaction. To solve this problem database system introduce concurrent scheduling.

Comments

Post a Comment

Popular posts from this blog

How to construct a B+ tree with example

Image
A B+ tree contains n-1 search key values K1K2…….Kn-1 and have n pointers.   In a B+ tree the data are ordered  sequentially.  The leaf node may hold up to n pointers and must hold at least N/2 pointers. The root node must hold at least two pointers, unless the tree consists of only one node.  Now we construct a B+ tree. Construct a B+ tree for the following set of key values: (2,3,5,7,11,17,19,23,29,31) Assume that the tree is initially empty and values are added in ascending order. Construct a B+ tree where the pointer number is Four. Solution: When a node exceeds n-1 search key value then we split it into two nodes. First node contains (ceiling(n-1)/2) values.  2 nd node contains remaining node. Copy the smallest search key value of the second node to the parent node. Let's start, we know each node has N pointer and has N-1 search key values. In our example pointer number is 4, so the search key value is 4-1=3. So each node has 4 pointers and 3 search key value. The first node i
Read more

How to show only month and year fields in android Date-picker?

Image
Android default DatePicker show day/month/year fields but you have to customize this DatePicker as your requirements. Suppose that you want to show only month and year fields in android datepicker . To do this, you have to customize the Dialog DatePicker source code but it is not an easy task. In this tutorial I will show you a tricky way to solve this problem. Lets see how to show only month and year field in android DatePicker as a dialog.   Step to show only month and year fields in android date-picker: Some days ago I got this same problem and here I am trying to explain this in a sequential manner. I want to show a dialog datepicker when user click on an EditText. So if user click on EditText, A dialog datepicker will be invocked and it will show only month and year fields. To do this, at first we have to create a xml layout to hold the EditText fields. So create an android project and name it DatePickerExample. In the main.xml file just try to write this simple code.  main.xml
Read more

Visitor Counter Script Using PHP

Image
If you have noticed that many websites display their total numbers of visitors.In this tutorial I am going to explain you how to create a simple visitor counter using php. For this, 1) Create one table called “visitor_counter” in your database. 2) Create file named “counter.php”. Step1: Creating “visitor_counter” Table CREATE TABLE `visitor_counter` ( `counts` int(10) NOT NULL default '0' ) Step2: Creating “counter.php” File <?php  // Database Details $host="localhost"; $username="root"; $password=""; $db_name="test"; $tbl_name="visitor_counter"; // Connect to server and select database. mysql_connect("$host", "$username", "$password")or die("cannot connect to server "); mysql_select_db("$db_name")or die("cannot select DB");  $sql="SELECT * FROM $tbl_name"; $result=mysql_query($sql); $rows=mysql_fetch_array($result); $counter=$rows['counts']; // se
Read more