The most common reason is that the Internet Guest account (IUSR_MACHINE), which is by default part of the "Everyone" group, does not have Write permissions on the database file (.mdb). To fix this problem, use the Security tab in Explorer to adjust the properties for this file so that the Internet Guest account has the correct permissions.
NOTE: When using Microsoft Access databases with ADO, it is also necessary to give the Internet Guest account Write permissions on the directory containing the .mdb file. This is because Jet creates an .ldb file to handle database locking. You may also need to give read/write permission on the "Temp" folder because Jet may create temporary files in this directory.
A second cause of this error is that the database was not opened with the correct MODE for writing. If you perform the Open on the Connection object, you use the Mode property to indicate the permissions on the connection as shown here:
SQL = "UPDATE Products Set UnitPrice = 2;"
Set Conn = Server.CreateObject("ADODB.Connection")
Conn.Mode = 3 '3 = adModeReadWrite
Conn.Open "myDSN"
Conn.Execute(SQL)
Conn.Close
NOTE: By default, the MODE is set to 0(adModeUnknown), which generally allows updates.
Another cause of this error is that the "Read Only" setting may be checked in the Options page for this DSN in the ODBC Manager.
The last issue and work around pertains to any SQL data source. The error can be caused by SQL statements that violate referential integrity of the database. Here are a few of the most common queries that fail:
The simplest groups to deal with are those you cannot change: crosstab, SQL pass-through, union, or update (or make-table) action queries that have UniqueValue properties set to Yes.
Another very common cause is when the join includes linked ODBC tables that do not have unique indexes. In this case, there is no way for SQL to guarantee that records are unique in a table that has fields whose value will change with the query.
One cause does have a robust workaround. If you try to update a join field on the "one" side of a "one-to-many" query it will fail unless you turn on cascading updates. This way, you delegate referential integrity to the JET engine.
