|
The setup dialogue provides for further optional settings under the Options tab:
|
|
Prefix: |
Search paths to be inserted in front of all relative file references used in Data Dictionary or INI definitions. Use a comma ’
,’ separator between multiple prefixes. The maximum length is 1023 characters.
|
|
Views DLL: |
Path to
pvxwin32.dll. This is required by the ODBC in order to use the Views system (ProvideX Version 5.10 or later).
|
|
Enforce Double: |
Checkbox to set default format of "double" for numeric data. This helps avoid conflicts with MS Office 2000 and other applications that do not support the decimal data type for numeric values. |
|
NULL Date: |
Checkbox to suppress invalid date error. The driver validates the contents of date columns at run time. If a value is invalid, the driver generates an error message and ceases processing of the table. This replaces an invalid entry with a null value and allows the driver to continue processing. |
|
Keys Restrict: |
Checkbox to restrict keys. This option allows the driver to be used with an application such as Lotus Approach 97, which does not support keys, or supports them with limitations on length, field segments, or use of sub-strings. |
|
Silent Mode: |
Checkbox to suppress most prompts or message boxes that the ODBC driver generates during processing. |
|
Cache Size: |
Establishes the amount of memory to use for local storage of intermediate results. If this value is zero, then intermediate information will not be cached locally on the workstation. Instead, it must be re-acquired from the server, which may lead to poorer performance on slower connections.
If a cache size is specified then that amount of system memory will be used to store information locally. Once the specified amount of memory is utilized, the driver will store additional information in a temporary disk file on the local workstation.
Performance gains will vary with the environment. In a high bandwidth environment (LAN), caching may not be as beneficial as in a low bandwidth environment (WAN), where the impact can be significant.
|
| |
|
| Performance Tuning |
The following options provide methods to reduce overhead when processing a file: |
|
Dirty Read: |
Checkbox for Dirty Read mode of operation to skip the normal file consistency checks. Dirty reads can speed file processing by reducing the number of locks issued against a file. However this may result in inconsistent data should the file be updated while being read by the ODBC driver. |
|
Burst mode: |
Checkbox to enable Burst mode. This helps reduce some of the overhead created by temporary locks. With Burst mode set, the ODBC driver locks the file header for either 50 file operations or three-tenths of a second, whichever occurs first. This decreases the number of times the file must be locked, and the number of times that internal buffers may need to be reloaded.
See the explanation below for more information on the effect of temporary locks.
|
|
Normally, when the ODBC driver accesses data files, it must place a temporary lock on the file. This temporary lock guarantees that the driver reads key tables and structures that are in a consistent state and not in the process of being altered.
Once the temporary lock is established, the driver checks the file header to see if it has been changed since the last time the file was accessed. If the file has not been altered, then the ODBC driver can use any of the data still maintained in its buffers. If the file has been altered, then all data in the buffers is discarded. When the driver has completed its access to the data file, the temporary lock is released.
The process is repeated for each file accessed by the driver, for each operation on the file.
|