c-treeDB API for VB.Net

Record/Row Locking

drivers\vb.nav\tutorials\Tutorial3.vb

Now we will explore row/record locks using the c-treeDB .NET Visual Basic NAV Framework.

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.

As with 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 FairCom Database Engine.
• Define() - Defines and creates a "customer master" (custmast) table/file.
• Manage() - Adds a few rows/records, manipulates them, and displays the results.
• Done() - Disconnects from FairCom Database Engine.

Note our simple Main() function:

Imports System

Imports FairCom.CtreeDb

Module Tutorial3HL

Dim MySession As CTSession

Dim MyTable As CTTable

Dim MyRecord As CTRecord

'

' main()

'

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

' and you're done..."

'

Sub Main()

Initialize()

Define()

Manage()

Done()

Console.WriteLine(ControlChars.NewLine + "Press <ENTER> key to exit . . .")

Console.ReadLine()

End Sub

In This Section Init Define Manage Done