ACC: Factors When Opening Attached ODBC Tables in MS Access

MORE INFORMATION

• When the attached table does not have a unique index in the data source.
  
  Microsoft Access is built on a keyset-driven cursor model, in which data is retrieved and updated based on key (or unique index) fields. If the key does not exist in the back-end table, Microsoft Access opens the table in read-only mode and the user is not able to modify the data.
• If the ODBC data source is set to read-only by either the DBMS security system or the network security system.
  
  Microsoft Access determines this status by calling the ODBC application programming interface (API) SQLGetInfo() with fInfoType=SQL_DATA_SOURCE_READ_ONLY. If *rgbInfoValue=TRUE, then the data source is read-only; as a result, the attached table is opened in read-only mode.
• If cursors are treated by the ODBC driver in a certain way. When a transaction is committed or rolled back, the ODBC driver can:
  
  
  1. Preserve the cursor.
  2. Close the cursor.
  3. Close and delete the cursor.
  A cursor is a construct that is defined to point to a record (or set of records) in the table. The data is then manipulated by referencing the cursor.
  
  If the driver exhibits behavior 3, Microsoft Access opens the table in read-only mode. To determines this, Microsoft Access first calls the ODBC API SQLGetInfo() with fOption=SQL_TXN_CAPABLE. If
  

  *rgbInfoValue=TRUE,

  Microsoft Access calls SQLGetInfo with
  

  fInfoType=SQL_CURSOR_COMMIT_BEHAVIOR

  followed by
  

  fInfoType=SQL_CURSOR_ROLLBACK_BEHAVIOR.

  If either of these values is 0, the ODBC driver closes and deletes the cursors on committals or rollbacks.