The
cursor type and lock type you specify when opening a recordset is important.
By default, the cursor type is a forward only moving cursor. This means
that it makes only one trip through your rows of data and cannot go
backwards. This type of cursor is called an adOpenForwardOnly cursor.
The default lock type is is called an adLockReadOnly lock type. What
this lock type does is that it only allows data to be read from, but
not altered. Therefore, if you need to update information in a record
in your database, you would need to use a different lock type. For most
ASP applications, the default cursor and locktypes will be fine. But
when you need to alter data, you will need to consider carefully which
cursor and lock type best fit your situation. Determining these types
have a direct effect on the performance of the server and therefore
your ASP pages. Here is the code for your recordset object and how the
cursor and lock types are used.
Set
RS = Server.CreateObject("ADODB.Recordset")
RS.Open tablename,
connectionname, cursortype, locktype,
adCmdTable
Cursor
Types
adOpenForwardOnly
An adOpenForwardOnly
cursor (as said above) only supports moving through a recordset in a
forward motion. It does not support backtracking through a recordset
and will only give you one time through the record. This method is the
default because it is the fastest cursor to use.
adOpenStatic
An adOpenStatic
cursor is different than an adOpenForwardOnly in that it can move backwards
through the data. It cannot however, tell whether any data has been
modified since the last time through.
adOpenKeyset
The adOpenKeyset
cursor is one better than the adOpenStatic in that it can detect whether
data has been updated. It supports backwards scrolling through the content,
but it cannot tell whether any rows have been deleted. This can leave
a hole in your recordset.
adOpenDynamic
An adOpenDynamic
cursor is the most flexible cursor available to use. It fully supports
scrolling and it also can detect any changes to the data since the last
past through. This, however, is the slowest cursor to use.
Lock
Types
adLockReadyOnly
An adLockReadOnly
is the default lock type. It allows multiple users to read the same
data at the same time, but does not allow any altering of this data.
adLockPessimistic
An adLockPessimistic
lock type prevents anyone from accessing your data as soon as you start
editing it.
adLockOptimistic
An adLockOptimistic
lock type allows others to access the data only until it any updates
have been added.
adLockBatchOptimistic
An adLockBatchOptimistic
lock type is used when making batch updates.
If all you are trying
to do is simply display data from your database, then you should use the
default lock type. However, if you are updating any data, the most recommended
lock type is adLockOptimistic because it still allows other users to view
the data until you make your update and therefore causes the least amount
of inconvenience and interferance. I hope this has helped to clear up
any questions regarding the lock and cursor type of the recordset object.
See ya next time!
