Microsoft KB Archive/170129

= PRB: Update Conflict When Updating Oracle Varchar Data Types =

Article ID: 170129

Article Last Modified on 11/7/2000

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APPLIES TO


 * Microsoft Visual FoxPro 5.0 Standard Edition
 * Microsoft Visual FoxPro 5.0a
 * Microsoft Visual FoxPro 6.0 Professional Edition

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This article was previously published under Q170129



SYMPTOMS
When updating a remote view based on an Oracle table that contains fields of type "varchar," you may receive an Update Conflict error.



CAUSE
When a remote view retrieves data from the Oracle backend, all varchar fields are converted to character fields. Visual FoxPro pads the character fields with spaces to accommodate the overall length of the varchar field.

The Update Conflict occurs as a result of a mismatch in the SQL WHERE clause criteria due to the padded spaces. For example: if an Oracle table has a varchar(5) field with a value of "aaa". the actual value that the remote view uses in the SQL WHERE clause is "aaa ". The Update Conflict occurs because "aaa"<>"aaa ".

NOTE: This occurs when the varchar field size is less than the default set in the 'Use Memo Fields for Fields <=:' setting in Tools/Options/Remote Data. Any Oracle varchar field with a size greater than this setting will be viewed as a memo field.



RESOLUTION
Here are two possible methods you can use to avoid the Update Conflict:


 * Set the SQL WHERE clause option in the Update Criteria such that no varchar fields are included in the SQL WHERE clause. In other words, select the option button choice, "Key fields only".

NOTE: The following documentation is in the Visual FoxPro Help topic, "Update Criteria Tab, View Designer" as follows:

SQL WHERE Clause Includes

Controls which fields are added to the WHERE clause to detect update conflicts on the server when the changes to the view are sent to the original tables.

A conflict is based on a comparison between the old values in the view, OLDVAL, and the current values in the original table, CURVAL. If the values are equal, the original table is considered unchanged and no conflict exists. If they are not equal, a conflict exists and the data source returns an error.

The error returned for a conflict between the old value and the current value is Error 1585 "Record has been modified by another" or Error 1494 "Update conflict. Use TABLEUPDATE to force the update or TABLEREVERT to rollback".

Key Fields Only: Sets the WHERE clause to detect a conflict if a key field has been changed in the original table. Changes made by another user to any other field in the original record of the table are not compared.

Key and Updatable Fields: Sets the WHERE clause to detect a conflict if another user changed any of the fields that were updatable.

Key and Modified Fields: Sets the WHERE clause to detect a conflict if the key field or one of the modified fields in the record in the original table has changed since the view was first retrieved (default).

Key and Timestamp: Sets the WHERE clause to detect a conflict if the timestamp of the record on the original table has changed since it was first retrieved. This option is only available if the remote table has a timestamp column.

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 * Change the data type of all the varchar fields to Memo. You can do this by clicking the Properties button on the Fields tab of the Remote View Designer.



Steps to Reproduce Behavior

 * 1) Create an Oracle table that contains at least one varchar field.
 * 2) Create a remote view based on the Oracle table created in step 1.
 * 3) Make the varchar field updateable and set the SQL WHERE clause option to "Key and modified."
 * 4) Browse the view, and make a change to the varchar field.
 * 5) Close the view.

NOTE: The Update Conflict error occurs.

Keywords: kberrmsg kbprb KB170129

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