Record/Row Locking

..\sdk\sql.jdbc\tutorials\JDBC_Tutorial3.java

Now we will explore row/record locks using the c-treeACE SQL JDBC Interface.

The functionality for this tutorial focuses on inserting/adding rows/records, then updating a single row/record in the customer master table under locking control. The application will pause after a LOCK is placed on a row/record. Another instance of this application should then be launched, which will block, waiting on the lock held by the first instance. Pressing the <Enter> key will enable the first instance to proceed. This will result in removing the lock thereby allowing the second instance to continue execution. Launching two processes provides a visual demonstration of the effects of locking and a basis for experimentation on your own.

Like all other examples in the c-tree tutorial series, this tutorial simplifies the creation and use of a database into four simple steps: Initialize(), Define(), Manage(), and you’re Done() !

Tutorial #3: Locking

Here we demonstrate the enforcement of data integrity by introducing record/row "locking".

• Initialize() - Connects to the c-treeACE Database Engine.
• Define() - Defines and creates a "customer master" (custmast) table/file.
• Manage() - Adds a few rows/records; Reads the rows/records back from the database; displays the column/field content. Then demonstrates an update operation under locking control, and a scenario that shows a locking conflict.
• Done() - Disconnects from c-treeACE Database Engine.

Note our simple mainline:

import java.sql.*;

import java.io.*;

public class JDBC_Tutorial3 {

   static Connection conn;

   static Statement stmt;

   //

   // main()

   //

   // The main() function implements the concept of "init, define, manage

   // and you're done..."

   //

   public static void main (String[] args)

      throws java.io.IOException

   {

      Initialize();

      Define();

      Manage();

      Done();

      System.out.print("\nPress <ENTER> key to exit . . .");

      System.in.skip(1);

      System.in.read();

      System.exit(0);

   }

We suggest opening the source code with your own editor.

Continue now to review these four steps.