The Connection Object - The ConnectionTimeout Property and More
(Page 8 of 15 )
This property indicates how long, in seconds, to wait while trying to establish a connection before aborting the attempt and generating an error. The default is 15 seconds.
Long = Connection.ConnectionTimeout
Connection.ConnectionTimeout = Long
If the timeout period expires before the connection opens, an error is generated and the connection cancelled. Setting this property to zero will force the provider to wait indefinitely.
You cannot set this property once the connection has been established.
The CursorLocation Property This property sets or returns the location of the cursor engine.
CursorLocationEnum = Connection.CursorLocation
Connection.CursorLocation = CursorLocationEnum
You can set this property to one of the following CursorLocationEnum values:
- adUseClient, to use a client-side cursor
- adUseClientBatch, to use a client-side cursor
- adUseServer, to use a server-side cursor
- adUseNone, to indicate no cursor services are used (included for backward compatibility and should not be used)
A disconnected recordset can be achieved only by setting the CursorLocation property to adUseClient.
A Recordset created against the Connection object will inherit the value set here.
Changing the CursorLocation property has no effect on existing Recordsets associated with a Connection. The performance issues surrounding various cursor types are discussed in Chapter 14.
The DefaultDatabase Property This property indicates the default database for a Connection object.
String = Connection.DefaultDatabase
Connection.DefaultDatabase = String
You can access objects in other databases by fully qualifying the objects, if the data source or provider supports this.
For example, when using Microsoft SQL Server, you can create two recordsets on different databases:
objConn.DefaultDatabase="pubs"
rsOne.Open "authors", objConn, _
adOpenKeyset, adLockReadOnly, adCmdTable
rsTwo.Open "Sales.dbo.Orders", objConn, _
adOpenKeyset, adLockReadOnly, adCmdTable
The first uses the authors table from the default pubs database, and the second uses the Orders table in the Sales database. Note that this option is not available when using the RDS client-side Connection objects.
The IsolationLevel Property This property indicates the level of transaction isolation for a Connection object.
IsolationLevelEnum = Connection.IsolationLevel
Connection.IsolationLevel = IsolationLevelEnum
The isolation level allows you to define how other transactions interact with yours, and whether they can see your changes and vice versa.
This value comes into effect only when you call the BeginTrans method. The provider may return the next greater level of isolation if the requested level is not available.
The value can be one of the IsolationLevelEnum constants:
- adXactUnspecified indicates that the provider is using a different isolation level to the one you specified, but it cannot determine which level.
- adXactChaos indicates that a higher-level transaction has control over the records. This means that you cannot overwrite any pending changes from another user.
- adXactBrowse or adXactReadUncommitted allows you to view uncommitted changes in another transaction. Be careful when using either of these values, because the changes in another transaction have not been committed; therefore, they could be rolled back, leaving you with invalid values.
- adXactCursorStability or adXactReadCommitted (the default) indicates that you can view changes in other transactions only after they have been committed. This guarantees the data’s state. However, new records and deleted records will be reflected in your recordset.
- adXactRepeatableRead doesn’t allow you to see changes made from other transactions unless you re-query the recordset. Once you have re-queried the recordset, you can see new records that might have been added by other users to the records that compose your recordset.
- adXactIsolated or adXactSerializable indicates that transactions are completely isolated from each other. This means that all concurrent transactions will produce the same effect as if each transaction were executed one after the other.
 This is from ADO Programmer's Reference, by Dave Sussman (Apress, ISBN 1590593421). Check it out at your favorite bookstore today. Buy this book now. |
Next: The Mode Property and Provider Property >>
More ASP.NET Articles
More By Apress Publishing
/ 19 
