INFO: MDAC Upgrade Issues with Access ODBC Driver

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Summary

Microsoft Data Access Components (MDAC) versions 2.1 and 2.5 both install a major new version of the Microsoft Access ODBC driver. This Access ODBC driver uses the Microsoft Jet 4.0 database engine, which allows access to Access 2000 format databases as well as to all previous Access database formats. The version of the Access ODBC driver that ships with MDAC version 1.5 and 2.0 uses the Microsoft Jet 3.5 database engine to manipulate the Access database file.

Due to design changes in Jet 4.0, as well as issues with backward compatibility, the new Access ODBC driver can break existing, installed ODBC applications that use the Access ODBC driver, in some cases forcing the developer to recode the application.

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Overview of MDAC 2.1 and MDAC 2.5 Access ODBC Driver Issues

The Jet 4.0-based Microsoft Access ODBC driver uses the same file name as the older Jet 3.5-based driver, namely Odbcjt32.dll. When you install MDAC 2.1 or 2.5, the Jet 3.5-using Odbcjt32.dll file is overwritten by a Jet 4.0-using Odbcjt32.dll ODBC driver Dll. Thus, existing installed applications that use the Microsoft Access ODBC driver that shipped with MDAC 2.0 or MDAC 1.5 are converted to the newer driver if MDAC 2.1 or MDAC 2.5 is installed on the computer.

Odbcjt32.dll is the core Microsoft Access ODBC driver DLL. This DLL exports all of the ODBC API functions used by an ODBC client application. When you use Odbcjt32.dll from ODBC, it loads and uses either Msjet35.dll or Msjet40.dll (Jet 3.5 or Jet 4.0) to manipulate the Access database. Note that if you install MDAC 2.0 and then install MDAC 2.1 or MDAC 2.5 on the same computer, you have two parallel functioning versions of Jet installed on the computer because all of the Jet engine files have unique file names between Jet 3.5 and Jet 4.0. However, since the new Odbcjt32.dll installed by MDAC 2.1 or MDAC 2.5 is wired to use the new version of Jet, the older Jet 3.5 DLLs are no longer used by the Access ODBC driver.

To determine which version of the Microsoft Access ODBC driver is installed, open the ODBC Administrator and click on the Drivers tab. Examine the version number of the driver named "Microsoft Access Driver (*.mdb)". If the version starts with 3.5, you are using the Access ODBC driver that is hard-wired to use Jet 3.5. If the version starts with 4.0, you are using the Access ODBC driver that is hard-wired to use Jet 4.0.

Listing of Backward Compatibility Issues with the Microsoft Access ODBC Driver that Ships with MDAC 2.1, MDAC 2.1 SP1, MDAC 2.1 SP2, MDAC 2.5, MDAC 2.5 SP1

  1. The MDAC 2.1 and MDAC 2.5 version of the Access ODBC Driver does not write to older format-replicated databases. If you have an Access design master or replica database in Access 97 format (or Access 95 format), the MDAC 2.1 (or MDAC 2.5) Access ODBC driver can open this database, but only in read-only mode. In order to both read and write with ODBC, you need to use the Microsoft Access ODBC driver that shipped with MDAC 2.0. The error reported when attempting to update an older format replica database is "Operation not supported on replicable databases that have not been converted to the current version." Workarounds include converting the database to Access 2000 format, dropping back to the MDAC 2.0 SP2 version of the ODBC driver, or unreplicating the database.
  2. The Paradox ODBC driver that ships with MDAC 2.1 and MDAC 2.5 is read-only unless the Borland Database Engine (BDE) is installed. See the following article in the Microsoft Knowledge Base article for more information:
    230126 ACC2000: Using Paradox Data with Access 2000 and Jet
    However, Microsoft has created new Paradox ISAM drivers for Microsoft Jet 4.0 that do not require the installation of the BDE to provide full read/write access to Paradox files. See the following article in the Microsoft Knowledge Base article for more information:
    263561 INFO: Non-BDE Paradox and dBase ISAM Drivers
  3. The dBase ODBC driver that ships with MDAC 2.1 and MDAC 2.5 is read-only unless the BDE is installed. See the following article in the Microsoft Knowledge Base article for more information:
    230125 ACC2000: Using dBASE Data with Access 2000 and Jet
    However, Microsoft has created new dBase ISAM drivers for Microsoft Jet 4.0 that do not require the installation of the Borland Database Engine (BDE) to provide full read/write access to dBASE files. See the following article in the Microsoft Knowledge Base article for more information:
    263561 INFO: Non-BDE Paradox and dBase ISAM Drivers
  4. Installing MDAC 2.1 or MDAC 2.5 may break all applications that use the Microsoft FoxPro ODBC driver. Developers need to switch to the Visual FoxPro ODBC driver. See the following article in the Microsoft Knowledge Base article for more information:
    235357 PRB: FoxPro ODBC Driver Replaced by Visual FoxPro ODBC Driver
  5. Customers have reported several major performance issues with the Microsoft Access ODBC driver that ships with MDAC 2.1 and later. Performance drops of up to 400% between the Jet 3.5-based ODBC driver and the Jet 4.0-based ODBC driver have been reported.

    Reported issues include slower connection opens (SQLConnect), slower SQL command executions (SQLExecDirect), slower record insertions when using date/time fields, slower scrolling (SQLSetPos), and slower data retrieval (SQLGetData) performance. The following Knowledge Base article discusses these issues:
    168686 PRB: Performance Loss When Upgrading Jet ODBC Driver
  6. The newer Access ODBC driver now follows the ANSI 92 SQL specification, because Jet 4.0 follows this specification. This can cause SQL statements that worked properly with the Jet 3.5-based ODBC driver to fail to produce the desired results. The following Knowledge Base articles detail these issues:
    237992 PRB: Query Testing for NULL in Access Database Does Not Return Records with Jet 4.0
  7. There is a known bug in SQLBindCol where a memory leak occurs with the MDAC 2.1 version of the Access ODBC Driver. This issue is fixed in MDAC 2.1 SP2.
  8. Inserting data into a Bit (Yes/No) field in a Microsoft Access database results in the bit field being always False, even when a value of True is specified. This issue is fixed in MDAC 2.1 SP2; see the following Knowledge Base article for more details:
    221184 FIX: Access Bit Fields and MDAC 2.1
  9. After installing the newer Access ODBC driver, deleting a record from a keyset or dynamic cursor results in the row position becoming out of synchronization. For example, after a delete you are supposed to be on record 5 but you end up on record 10. This issue is fixed in MDAC 2.1 SP2; see the following Knowledge Base article for more details:
    230131 Access ODBC Keyset Cursor Becomes Corrupt After a Delete
  10. Both MDAC 2.1 and MDAC 2.5 versions of the Access ODBC driver report unexpected column lengths for text columns when calling SQLColumns. See the following Knowledge Base article for more details:
    236871 BUG: SQLColumns Return Incorrect BUFFER_LENGTH/CHAR_OCTET_LENGTH
  11. The MDAC 2.1 Access ODBC driver is not compatible with earlier versions regarding the usage of SQL_ATTR_NOSCAN (SQL_NOSCAN). The MDAC 2.1 Access ODBC driver continues to preparse ODBC escape sequences even if it is turned off by ODBC API calls.

    This problem is fixed with the MDAC 2.5 Access ODBC driver.
  12. The MDAC 2.1 and MDAC 2.5 Access ODBC drivers do not support the usage of literal GUIDs in SQL statements. The MDAC 2.0 Access ODBC driver supports literal GUIDs in SQL statements when ODBC escape sequence preparsing is turned off. See the following Knowledge Base article for more details:
    170117 HOWTO: Use GUID Fields in Access from Visual C++
  13. Both MDAC 2.1 and MDAC 2.5 Access ODBC Drivers break backward compatibility with usage of the LIKE clause. This is a rare issue where a text field contains the caret character ('^') and you try to select the field using a like clause. For example, if a field f1 contains the value 'C^C' and you attempt to select the record using the following SQL statement, the record is not be selected:
    SELECT * FROM Test WHERE f1='C^C'
    					
  14. With the Access ODBC driver that ships with MDAC 2.1 and MDAc 2.5, double quotes can no longer be used as string literals in SQL statements. For example, the following SQL statement works properly with the MDAC 2.0 driver but returns an error ([Microsoft][ODBC Microsoft Access Driver] Too few parameters. Expected 1.) when using the MDAC 2.1 driver:
    SELECT "Test" AS F1 FROM Test
    						
    Using single quotes for string literals works with both drivers.
  15. Customers have reported database bloating issues with the MDAC 2.1 and MDAC 2.5 versions of the Access ODBC driver. Jet 4.0 now stores all text data as Unicode, and this can require twice as much space as ANSI text (two times the amount of bloating due to Unicode storage of data). Also, there is a record locking issue with MDAC 2.1 that is fixed by installing MDAC 2.1 SP2. See the following Knowledge Base article for more details:
    239527 ACC2000: Database Bloats When Importing Large Text File
  16. Both MDAC 2.1 and MDAC 2.5 versions of the Access ODBC driver may return invalid ordinals when calling SQLColumns. If you create a table in Access and later remove a column, the column ordinals reported by the Access ODBC driver when calling SQLColumns are not in sequence. For example, if you create a table with 4 columns and then delete column 2, the reported column ordinals are 1,3,4 rather than 1,2,3. According to the ODBC specification (SQLColumns, ORDINAL_POSITION), the ordinal positions of the columns must start with 1 and must be in sequence.
  17. Both MDAC 2.1 and MDAC 2.5 versions of the Access ODBC driver rename some native data types from the previous version. If you call SQLGetTypeInfo, the following type names are renamed:
        MDAC 2.0 Name    MDAC 2.1 and MDAC 2.5 Name
        -------------   ----------------------------
         LONGTEXT             LONGCHAR
         LONG                 INTEGER
         TEXT                 VARCHAR
    					
  18. The MDAC 2.1 Access ODBC driver reported an incorrect column length when calling SQLDescribeCol on a calculated textual field. For example, if you submitted the following SQL statement, SQLDescribeCol returns 2147483598 as the length of calculated column and not the expected 255 (standard length of text column reported by the MDAC 2.0 Access ODBC driver):
    SELECT [CompanyName] + [ContactName] AS x FROM Customers
    						
    This bug is fixed in MDAC 2.1 SP1 and all later MDAC 2.1 service packs.
  19. When using the MDAC 2.1 or MDAC 2.5 Access ODBC driver with SQLConfigDataSource and REPAIR_DB, the call fails if the database name is not enclosed in double quotes. With the MDAC 2.0 driver the double quotes are not needed. This issue is fixed in MDAC 2.1 SP2.
  20. When using the MDAC 2.1 or MDAC 2.5 version of the Microsoft Access ODBC driver and opening a Microsoft Access database file on a network share, an excessive amount of network packet activity occurs, even when the ODBC connection is idle. This is due to the newer driver interpreting the PageTimeout setting correctly (whereas the MDAC 2.0 driver interpreted it incorrectly).For additional information, click the article number below to view the article in the Microsoft Knowledge Base:
    246560 BUG: Excessive Network Activity When Using Access ODBC Driver
  21. With both MDAC 2.1 and MDAC 2.5 Access ODBC drivers, using the SQL keyword TEXT without a length specifier in DDL now maps to a memo field (with the MDAC 2.0 driver, TEXT would map to TEXT(255)). For example, the following SQL statement creates a TEXT(255) field with the MDAC 2.0 driver and a MEMO field when using the MDAC 2.1 driver:
    CREATE TABLE Test (f1 TEXT)
    					
  22. When executing a parameterized query that contains a subquery with the MDAC 2.1 or MDAC 2.5 version of the Access ODBC Driver, parameter markers are processed in an unexpected order. Rather than processing the parameter markers from left to right as they appear in SQL, the parameter markers in the subquery are processed first, and then the main query parameter markers are processed. See the following Knowledge Base article for more information:
    244719 FIX: Parameter Mismatch with Sub queries When Using Access ODBC
    This problem was corrected in Microsoft Jet 4.0 Service Pack 4.
  23. When you open and close multiple statements under a single HDBC while using Microsoft Access ODBC Driver (both MDAC 2.1 and MDAC 2.5 versions), memory usage climbs until you close the parent HDBC. Also, when you open and close multiple rowsets under a single session while using Microsoft Jet OLE DB Provider 4.0, memory usage climbs until you release the parent session. The memory usage issue can be reproduced using ADO, ODBC, or OLE DB as the client API. See the following Microsoft Knowledge Base article for more information:
    247140 Memory Use Climbs with Multiple Recordsets Under a Single Jet Session

Starting with Microsoft Data Access Components (MDAC) version 2.6, MDAC no longer contains the following Jet components:
  • Microsoft Jet
  • Microsoft Jet OLE DB Provider
  • ODBC Desktop Database Drivers

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Article ID: 237994 - Last Review: June 19, 2014 - Revision: 4.0
Keywords: 
kbexcel123quattro kbgrpdsmdac kbgrpdsodbc kbjet kbmdac kbodbc kboledb kbprovider KB237994
Retired KB Content Disclaimer
This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.

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