Initializing the Microsoft Jet 2.5 Database Engine Driver
When you install the Microsoft® Jet version 2.5 Engine database driver, the Setup program writes a set of default values to the Microsoft Windows® Registry in the Engines and ISAM Formats subkeys. You must use the Registry Editor to add, remove, or change these settings. The following sections describe initialization and ISAM Format settings for the Microsoft Jet Engine database driver.
Microsoft Jet Engine Initialization Settings
The Jet\4.0\Engines\Jet 2.x folder includes initialization settings for the msrd2x40.dll driver, used for access to Microsoft Access 2.0 worksheets. Typical initialization settings for the entries in this folder are shown in the following example.
win32=<path>\ msrd2x40.dll
PageTimeout=5
LockedPageTimeout=5
CursorTimeout=5
LockRetry=20
CommitLockRetry=20
MaxBufferSize=512
ReadAheadPages=16
IdleFrequency=10
ForceOsFlush = 0
The following entries are used to configure the Microsoft Jet database engine.
| Entry | Description |
|---|---|
| win32 | Location of the database engine driver (.dll). The path is determined at the time of installation. Values are of type String for Windows 95 and Windows NT 4.0, and of type REG_SZ for Windows NT 3.51. |
| PageTimeout | The length of time between when data that is not read-locked is placed in an internal cache and when it is invalidated, expressed in 100 millisecond units. The default is 5 units (or 0.5 seconds). Values are of type DWORD for Windows 95 and Windows NT 4.0, and of type REG_DWORD for Windows NT 3.51. |
| LockedPageTimeout | The length of time between when data that is read-locked is placed in an internal cache and when it is invalidated, expressed in 100 millisecond units. The default is 5 units (or 0.5 seconds). Values are of type DWORD for Windows 95 and Windows NT 4.0, and of type REG_DWORD for Windows NT 3.51. |
| CursorTimeout | The length of time a reference to a page will remain on that page, expressed in 100 millisecond units. The default is 5 units (or 0.5 seconds). This setting applies only to databases created with version 1.x of the Microsoft Jet database engine. Values are of type DWORD for Windows 95 and Windows NT 4.0, and of type REG_DWORD for Windows NT 3.51. |
| LockRetry | The number of times to repeat attempts to access a locked page before returning a lock conflict message. The default is 20 times; LockRetry is related to CommitLockRetry. Values are of type DWORD for Windows 95 and Windows NT 4.0, and of type REG_DWORD for Windows NT 3.51. |
| CommitLockRetry | The number of times the Microsoft Jet database engine attempts to acquire a lock on data to commit changes to that data. If the Microsoft Jet database engine cannot acquire a commit lock, changes to the data will be unsuccessful.
The number of attempts the Microsoft Jet database engine makes to get a commit lock is directly related to the LockRetry value. For each attempt made to acquire a commit lock, the Microsoft Jet database engine will make as many attempts as specified by the LockRetry value to acquire a lock. For example, if CommitLockRetry is set to 20 and LockRetry is set to 20, the Microsoft Jet database engine will try to acquire a commit lock as many as 20 times; for each of those attempts, the Microsoft Jet database engine will try to acquire a lock as many as 20 times, for a total of 400 attempts. The default value for CommitLockRetry is 20. Values are of type DWORD for Windows 95 and Windows NT 4.0, and of type REG_DWORD for Windows NT 3.51. |
| MaxBufferSize | The size of the database engine internal cache, measured in kilobytes (K). MaxBufferSize must be a whole number value between 9 and 4096, inclusive. The default is 512. Values are of type DWORD for Windows 95 and Windows NT 4.0, and of type REG_DWORD for Windows NT 3.51. |
| ReadAheadPages | The number of pages to read ahead when performing sequential scans. The default is 16. Values are of type DWORD for Windows 95 and Windows NT 4.0, and of type REG_DWORD for Windows NT 3.51. |
| ForceOSFlush | Any setting other than 0 means a commit or a write will force flushing the OS cache to disk. A setting of 0 (the default setting) means no force flush occurs. Values are of type DWORD for Windows 95 and Windows NT 4.0, and of type REG_DWORD for Windows NT 3.51. |
| IdleFrequency | The amount of time, in 100 millisecond units, that Microsoft Jet will wait before releasing a read lock. The default is 10 units or one second. Values are of type DWORD for Windows 95 and Windows NT 4.0, and of type REG_DWORD for Windows NT 3.51. |
Microsoft Jet Engine ISAM Formats
The Jet\4.0\ISAM Formats\Jet 2.x folder contains the following entries.
Entry name |
Windows NT 3.51 Type |
Windows 95 and Windows NT 4.0 Type |
Value |
|---|---|---|---|
| Engine | REG_SZ | String | Jet 2.x |
| OneTablePerFile | REG_BINARY | Binary | 00 |
| IndexDialog | REG_BINARY | Binary | 00 |
| CreateDBOnExport | REG_BINARY | Binary | 00 |
| IsamType | REG_DWORD | DWORD | 0 |
Note When you change Windows Registry settings, you must exit and then restart the database engine for the new settings to take effect.
See Also
Customizing Windows Registry Settings for Microsoft Jet