ONLINE HELP
 WINDEVWEBDEV AND WINDEV MOBILE

Help / WLanguage / Managing databases / HFSQL / HFSQL functions
  • Managing locks
  • HSecurity and HFlush
WINDEV
WindowsLinuxUniversal Windows 10 AppJavaReports and QueriesUser code (UMC)
WEBDEV
WindowsLinuxPHPWEBDEV - Browser code
WINDEV Mobile
AndroidAndroid Widget iPhone/iPadIOS WidgetApple WatchMac CatalystUniversal Windows 10 App
Others
Stored procedures
HFlush (Function)
In french: HForceEcriture
HFSQL ClassicHFSQL Client/ServerAvailable only with these kinds of connection
Forces the operating system of the computer where the data files are found to write data onto the disk. The HFSQL context of the data file used is stored (lock, current browse, ...).
Remark: Used on a regular basis, this function minimizes the loss of data caused by the unexpected system outage on the computer where the data files are located (power failure for example).
Java This function is available for HFSQL data files only. It is not available for the data files accessed by JDBC.
Example
// Add a record in a data file
// (record described through programming)
Customer.LastName = "Clark"
Customer.FirstName = "Vince"
Customer.Address = "Palm lane"
Customer.City = "San Francisco"
Customer.Zip = "94102"
Customer.Country = "USA"
HAdd(Customer)
// Forces a write operation into Customer file
HFlush(Customer)
Syntax
HFlush(<Data file>)
<Data file>: Character string
Name of the data file used.
If this name is not specified, HFlush will use the last data file used by the last HFSQL function (function starting with "H").
If this parameter corresponds to "*", HFlush will be applied to all open data files.
Caution: In this case, the execution of function can be quite long.
This parameter can also correspond to the name of a group of files (or custom-folder) defined in the analysis (not available in Android and Android widget).
Remarks
WINDEVWEBDEV - Server codeReports and QueriesUniversal Windows 10 AppiPhone/iPadUser code (UMC)AjaxHFSQL ClassicHFSQL Client/Server

Managing locks

During the call to HFlush, the data file used is closed and re-opened. If locks were implemented on this data file before it was closed, these locks are automatically restored when it is re-opened. Indeed, when closing a data file, the operating system deletes the locks implemented on this data file.
Remark: It is not advisable to call this function too often on:
  • data files on which an important number of locks is implemented.
  • data files on which an important number of write operations is implemented.

HSecurity and HFlush

HSecurity and HFlush can both be used to force a physical write operation on disk.
However:
  • HSecurity is used to force a write operation into the data files used during each write operation. The HFSQL engine automatically performs the write operation. The data files are not closed during this write operation. This results in slower write speeds.
  • HFlush forces the data file(s) to be written when it is called. The data files are closed and then re-opened during this write operation. The write operation is not slowed down.
Component: wd300hf.dll
Minimum version required
  • Version 9
This page is also available for…
Comments
Click [Add] to post a comment

Last update: 06/06/2024

Send a report | Local help