ODBC - c-tree Plus Edition

Advanced - Registry Options

The c-tree Drivers set several Registry keys. Use the ConfigDSN() function to programmatically configure the c-tree ODBC Driver Data Source. Most c-tree Driver subkeys correspond to configuration entries shown in the table below. The other entries in this section are only adjustable in the Registry. All the subkeys below are in the key \\HKEY_CURRENT_USER\Software\ODBC\ODBC.INI\ <dname>, where <dname> defaults to one of the following:

• FairCom c-tree Driver for the c-tree V4 driver
• FairCom 32-bit Driver for the 32-bit c-tree Plus driver
• FairCom 16-bit Driver for the 16-bit c-tree Plus driver

Registry subkey	Configuration option
Alignment	Alignment
AllowUpdates	Allow Updates
CaseSensitive	Case-insensitive string Comparison
ColumnsOrderedBy	Column Order
CommEncryption	Use FETCPIP.DLL (deprecated) if Yes. Note: This DLL enables CAMO. CAMO or "Camouflage" is an older, legacy method of hiding data, which is not a standards-conforming encryption scheme, such as AES. It is not intended as a replacement for Advanced Encryption or other security systems.
DataBuffers	Data Buffer Size
DataDictionary	Script Name
DBQ	Data Dictionary Path
DebugCtree	c-tree Plus Debug
DebugIndex	Debug Indexes
Description	Description
EnableFPUExceptions	Not a configuration option. See below.
Files	Number of Files
ForceClose	Not a configuration option. See below.
GuestLogin	Logon to Server as Guest
IndexBuffers	Index Buffer Size
KanjiConvert	Not a configuration option. See below.
MaxColSupport	Table’s max number of columns
OEMtoANSI	OEM to ANSI Data Conversion
Protocol	Driver Type
Sectors	Sector Size
ServerName	Server Name
SpecialTypes	Special Data Type Conversion DLL Name
StringDataPadding	Data Padding
StringKeyPadding	Key Padding

It is also possible to use these keywords in a connection string that uses a DSN. The effect is to override the particular settings that are specified. For example: “DSN=FairCom 32bit Driver;Alignment=4;” uses the settings from the registry for the data source ‘FairCom 32bit Driver’ and forces the alignment setting to 4.

Note: Three registry settings (ForceClose, KanjiConvert, and EnableFPUExceptions) are not supported in the command string.

Adding a Shareable DSN

The Registry feature allows the creation and use of shareable file DSNs by the 32bit c-tree ODBC Driver. The Driver creates unshareable file DSNs automatically when creating user or system DSNs. To create a shareable file DSN:

1. Start the 32bit ODBC Administrator.
2. Select the File DSN tab.
3. Click the Add button.
4. Select the ODBC driver for which you wish to create a file DSN (either “FairCom 32bit ODBC Driver” or “FairCom c-tree Driver”).
5. Click the Advanced button and enter the desired driver-specific keywords (from the list above). Both DRIVER= (driver name) and DBQ= (data dictionary path) are required. For example:

DRIVER={FairCom 32bit ODBC Driver}

DBQ=c:\faircom\odbc\32bit

1. Click the OK button.
2. Click the Next button.
3. Enter the name of your new file DSN.
4. Click the Next button.
5. Click the Finish button.

If after you follow the above steps, the ODBC administrator returns the error “A connection could not be made using the file data source parameters entered. Save non-verified file DSN?”, you probably omitted needed parameters or specified invalid parameter values (see step 5 above). Click Cancel and start over at step 1.

After a file DSN is successfully created in this manner, it can’t be configured from the ODBC Administrator, however, it is a plain text file that can be edited to change its settings.

This type of file DSN is known as a shareable file DSN - if you arrange for it to be shared by multiple machines (each with the c-tree ODBC Driver installed), it will serve as an ODBC data source that is identically configured on all of these machines.

Force Close Option

For performance reasons, the c-tree ODBC Driver keeps data and index files open until the database is changed or the connection is closed. It is possible to force the Driver close files when the SQL engine requests files to be closed. To do so, create a registry key named ForceClose, as shown above, and set its value to “Yes” to enable this option.

Japanese two-byte character (EUC) support

Our Japanese customers requested that the c-tree Plus TCP/IP client code be able to support Japanese two-byte character (EUC) encoding. c-tree Plus supports this option when #define ctJAPANESE is enabled. The c-tree ODBC Driver - c-tree Plus Edition now supports this feature when the following key is added to the registry:

HKEY_CURRENT_USER\Software\ODBC\ODBC.INI\FairCom 32bit Driver\KanjiConvert=EUC

Specifying any value other than “EUC” disables this feature.

Optionally Disable Floating Point Unit Exceptions

By default, the c-tree ODBC Driver enables the divide by zero FPU (floating point unit) exception so that it can detect when a divide by zero error occurs. A customer requested the ability to avoid enabling this exception to work around a problem with Microsoft’s .Net Font class constructor, which raises an ArithmeticException exception if floating point unit exceptions have been enabled.

The c-tree ODBC Driver checks the registry for a string value named EnableFPUExceptions under the registry subkey:

HKEY_CURRENT_USER\Software\ODBC\ODBC.INI\FairCom 32bit Driver

If this string value exists and is set to No, the c-tree ODBC Driver does not enable FPU exceptions.