Tài liệu Back Up and Verify a SQL Server Database doc

This How-To shows you how to create a custom dialog box that will allow the user not only to back up your SQL Server database, but also to verify the backup.. Additional SQL-DMO Objects

7.2 Back Up and Verify a SQL Server Database

Backing up a database is probably one of the most important features to incorporate into your application If you leave it up to the user to use the Enterprise Manager to back up the database, then it won't happen You can arrange to have the backup scheduled, but sometimes you need to back it up at a moment's notice This How-To shows you how to create a custom dialog box that will allow the user not only to back up your SQL Server database, but also to verify the backup

Your users need to have a method for backing up and verifying their databases without using Enterprise Manager How do you create a dialog box that would let them back up and verify their databases?

Technique

To accomplish this task, you will once again use the SQL-DMO objects A couple of the new objects you will use are the Backup and BackupDevices objects You can see some

of the additional objects, along with the properties and methods that will be used, in Table 7.3

Table 7.3 Additional SQL-DMO Objects Used for Backing Up and Verifying a

Database Object Property/Method Description

Backup Action This property allows you to specify what type

of backup that you want to take place The choices are SQLDMOBackup_Database, SQLDMOBackup_Differential,

SQLDMOBackup_Files, and SQLDMOBackup_Log

BackupSetDescription This property allows you to specify a

description for the backup set

BackupSetName This property is the Backup set name

Database This property allows you to specify the

database to back up

Devices This property specifies the devices you will be

backing up to

Initialize This method initializes the Backup process TruncateLog This property allows you to specify how to

handle the truncate log when backing up

SQLBackup This method performs the actual backup

BackupDevices This is a collection of backup devices for a

SQL Server

BackupDevice Name Thisis the name of a specific backup device ReadBackupHeader This method reads in the header information

for a backup, returning a QueryResults object QueryResults ColumnName This is the individual property information

about a backup

GetColumnString This is the actual value for individual header

information

Using the objects listed in Table 7.3, you will create a form with options for the user to back up his database and verify the information after it has been saved

Note

Not all the possible options will be included in the form created for this How-To For example, you could allow the user to back up the database

to a separate file and give him additional options for the type of backup

to perform

Odds are good that you will not want to give the users all the options they could have; that is one of the reasons you want to create the dialog box here instead of letting users use the Enterprise Manager

Steps

Open and run the VB.NET -Chapter 7 solution From the main Windows form, click on the command button with the caption How-To 7.2

As with How-To 7.1, a user clicks on the SQL Server that he wants to display the

databases of He can then choose the database and backup device From there, the user can click the Backup button to perform the backup You can then click on the verify

button to have information about the backup displayed in the text box at the bottom of the form The form will look similar to the one displayed in Figure 7.7

1 Create a Windows Form Then place the controls shown in Figure 7.7, with the following properties set as in Table 7.4

Table 7.4 Controls and Their Property Settings

Command Button Name btnBackup

Radio Button Name rbFull

Radio Button Name rbIncremental

Radio Button Name rbNoLog

Radio Button Name rbNoTruncate

Radio Button Name rbTruncate

Scrollbars Both Command Button Name btnVerify

Command Button Name btnClose

2 On the form, add the code in Listing 7.8 to the Load event This will look familiar

to How-To 7.1 For an examination of the LoadSQLServers routine, check out step 4 in that How-To

Listing 7.8 frmHowTo7_2.vb: Calling the Routine That Loads Available SQL Servers into a List Box

Private Sub frmHowTo7_2_Load(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles MyBase.Load

' Load up the SQL Servers

LoadSQLServers(Me.lstSQLServers)

End Sub

3 On the lstSQLServers list box, add the code in Listing 7.9 to the

SelectedIndexChanged event This routine calls both the GetSQLDatabases, described in step 6 of How-To 7.1, and GetBackupDevices, described in the next step

Listing 7.9 frmHowTo7_2.vb: Populating the lstDatabases and

lstBackupDevices List Boxes

Private Sub lstSQLServers_SelectedIndexChanged(ByVal sender As

System.Object,

ByVal e As System.EventArgs) _

Handles lstSQLServers.SelectedIndexChanged

GetSQLDatabases(Me.lstSQLServers.SelectedItem, Me.lstDatabases)

GetBackupDevices(Me.lstSQLServers.SelectedItem, Me.lstBackupDevices) End Sub

4 Create the GetBackupDevices routine by entering the code in Listing 7.10 into the new module you created in How-To 7.1 The first task attempted by this routine is

to connect to the server that is selected Next, the names of the backup devices that are within the SQL Server are loaded into the list box called lstBackupDevices

Listing 7.10 modSQLDMORoutines.vb: Retrieving Backup Device Names for

a Given SQL Server

Public Sub GetBackupDevices(ByVal strSQLServer As String, _

ByRef lstBackupDevices As ListBox)

Dim oDevice As SQLDMO.BackupDevice

' Log on to the SQL Server

Dim osvr As SQLDMO.SQLServer = New SQLDMO.SQLServer()

osvr.LoginSecure = True

osvr.Connect(strSQLServer)

lstBackupDevices.Items.Clear()

' Iterate through the backup devices

For Each oDevice In osvr.BackupDevices

lstBackupDevices.Items.Add(oDevice.Name)

Next

End Sub

5 On the btnBackup button, add the code in Listing 7.11 to the Click event After connecting to the chosen SQL Server, a Backup object is instantiated Next,

certain properties of the Backup object, called oBackup, are set to values that are specified on the form The SQLBackup method is called off the Backup object, and the connection is closed Last, the variables are cleared (set to Nothing) and a message box is displayed

Listing 7.11 frmHowTo7_2.vb: Performing the Backup

Private Sub btnBackup_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles btnBackup.Click

' Create a connection to the server

Dim osvr As New SQLDMO.SQLServer()

osvr.LoginSecure = True

osvr.Connect(Me.lstSQLServers.SelectedItem)

' Create a Backup object, and set the necessary properties

' based on options chosen on the form

Dim oBackup As New SQLDMO.Backup()

With oBackup

If Me.rbFull.Checked Then

Action =

SQLDMO.SQLDMO_BACKUP_TYPE.SQLDMOBackup_Database

Else

Action =

SQLDMO.SQLDMO_BACKUP_TYPE.SQLDMOBackup_Differential

End If

BackupSetDescription = Me.txtBUSetDescription.Text

BackupSetName = Me.txtBUSetName.Text

Database = Me.lstDatabases.SelectedItem

Devices = "[" & Me.lstBackupDevices.SelectedItem & "]"

If Me.rbNoLog.Checked Then

TruncateLog = _

SQLDMO.SQLDMO_BACKUP_LOG_TYPE.SQLDMOBackup_Log_NoLog ElseIf Me.rbNoTruncate.Checked Then

TruncateLog = _

SQLDMO.SQLDMO_BACKUP_LOG_TYPE.SQLDMOBackup_Log_NoTrunca

te

Else

TruncateLog = _

SQLDMO.SQLDMO_BACKUP_LOG_TYPE.SQLDMOBackup_Log_Truncate End If

Initialize = Me.chkInitialize.Checked

' Execute the backup

SQLBackup(osvr)

End With

' Disconnect from the server and clean up

osvr.DisConnect()

osvr = Nothing

oBackup = Nothing

MessageBox.Show("Database Backed Up", "Task Completed", _

MessageBoxButtons.OK)

End Sub

6 Add the code in Listing 7.12 to the Click event of btnVerify After connecting to the SQL Server, the code iterates through each of the backup devices for the server and locates the one that the form specifies

After the specific backup device is located, the ReadBackupHeader method is called, with an SQLDMO.QueryResults object returned Each row of the

QueryResults is read, and then the information is displayed in a text box called txtVerifyDisplay From there, the SQLServer object is disconnected

Listing 7.12 frmHowTo7_2.vb: Performing the Backup

Private Sub btnVerify_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles btnVerify.Click

Dim oDevice As SQLDMO.BackupDevice

Dim oResults As SQLDMO.QueryResults

Dim intRowCount As Integer

Dim intColCount As Integer

' Create a connection to the server

Dim osvr As New SQLDMO.SQLServer()

osvr.LoginSecure = True

osvr.Connect(Me.lstSQLServers.SelectedItem)

' Iterate through the devices

For Each oDevice In osvr.BackupDevices

If oDevice.Name = Me.lstBackupDevices.SelectedItem Then

' If found, display the results

oResults = oDevice.ReadBackupHeader

For intRowCount = 1 To oResults.Rows

For intColCount = 1 To oResults.Columns

Me.txtVerifyDisplay.Text &= _

oResults.ColumnName(intColCount) & " - "

Me.txtVerifyDisplay.Text &= _

oResults.GetColumnString(intRowCount, _

intColCount) & vbCrLf & vbCrLf

Next

Next

End If

Next

' Disconnect and clean up

osvr.DisConnect()

osvr = Nothing

oDevice = Nothing

oResults = Nothing

End Sub

7 Add the code in Listing 7.13 to the Click event of btnClose

Listing 7.13 frmHowTo7_2.vb: Performing the Backup

Private Sub btnClose_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles btnClose.Click

Me.Close()

End Sub

Figure 7.7 Creating a form for backing up and verifying a SQL Database gives you

control over what options the user has when performing the task

How It Works

After the form loads, the user can select the SQL Server, database, and backup device When the user clicks the button labeled Perform Backup, a SQLDMO Backup object is created The Backup object gives you the same capabilities as if you were using the Enterprise Manager-except that you control them Only put options on the form that you want to have the user set, and then set the other options yourself, as you deem necessary After setting the options, the SQLBackup method performs the backup

By using the QueryResults object off the BackupDevice, you have a means of looking at some of the properties of the backup and verifying them to make sure the database did indeed get backed up

Comments

You could enhance this utility in a number of ways, a couple of which include the

following:

• Add a text box for letting the user specify a filename for the backup, rather than

using a backup device

• Allow the user to add backup devices Currently, only existing backup devices can

be used

Just be careful on what options you give the user so he doesn't shoot himself in the foot