HLockRecNum (Function)

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Modifying the type of lock for a record

Effect of lock mode

Lock failure

Number of locks

Native SQL Server Connector: Lock in write mode

Managing locks in OLE DB

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Modifying the type of lock for a record
Effect of lock mode
Lock failure
Number of locks
Native SQL Server Connector: Lock in write mode
Managing locks in OLE DB
Persistence of lock

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HLockRecNum (Function)

In french: HBloqueNumEnr

Not available with these kinds of connection

Locks a record and restricts the access to this record for all the other applications. Then, the record can be unlocked by HUnlockRecNum.

Remark: Several cases may occur after the call to HLockRecNum:

The record is already locked by another application: the lock cannot be performed.
The data file containing the record is entirely locked: the lock cannot be performed.

An automatic management of lock errors and modification conflicts is performed by default (except in the code of stored procedures). This assisted management of errors can be customized or disabled at any time by HOnError.

HErrorLock returns True if a lock problem occurs.

Caution: HLockRecNum must be used with great care: indeed, during the lock, the record is not re-read. Therefore, it may have been deleted or modified since the last access to this record. We recommend that you use HRead with lock option.

This function can be used with HFSQL Client/Server data files or with data files handled by Native Connectors. This function is not available for HFSQL Mobile.

Versions 16 and later

This function is now available for the Java applications.

This function is available for HFSQL data files only. It is not available for the data files accessed by JDBC.

New in version 16

This function is now available for the Java applications.

This function is available for HFSQL data files only. It is not available for the data files accessed by JDBC.

This function is now available for the Java applications.

This function is available for HFSQL data files only. It is not available for the data files accessed by JDBC.

Versions 17 and later

This function is now available for iPhone/iPad applications.

New in version 17

This function is now available for iPhone/iPad applications.

Versions 18 and later

This function is now available in Android Widget mode.

This function is now available for Android applications (for HFSQL data files).

This function is now available in Windows Store apps mode.

New in version 18

This function is now available in Android Widget mode.

This function is now available for Android applications (for HFSQL data files).

This function is now available in Windows Store apps mode.

This function is now available in Android Widget mode.

This function is now available for Android applications (for HFSQL data files).

This function is now available in Windows Store apps mode.

Versions 21 and later

This function is now available in Universal Windows 10 App mode.

New in version 21

This function is now available in Universal Windows 10 App mode.

Remark: From version 19, HFSQL is the new name of HyperFileSQL.

Example

// Lock a record in the Customer data file
HLockRecNum(Customer, hCurrentRecNum, hLockReadWrite)
// Process on the record
...
// Restore access to the record
HUnlockRecNum()

Syntax

<Result> = HLockRecNum([<Data file> [, <Record to lock>]] [, <Lock>])

<Result>: Boolean

True if the operation was performed,
False if a problem occurred. HError is used to identify the error.

<Data file>: Optional character string (with or without quotes)

Name of data file used.
If this name is not specified, HLockRecNum will use the last data file used by the last HFSQL management function (starting with "H").

<Record to lock>: Optional integer

Number of the record to lock.
If this parameter is not specified, HLockRecNum handles the current record.
HLockRecNum locks the current record only. You cannot specify a record number other than the current one (to specify the current record number, use the hRecNumCurrent constant).

<Lock>: Optional integer constant

Used to define the type of lock performed on the record.
hLockWrite
(default value) Lock in write mode: the record found in the data file can be read by another application but it cannot be modified by another application.
No lock on the record or on the data file can be defined by another application.
hLockReadWrite Lock in read/write: the record found in the data file cannot be read or modified by another application.
No lock on the record or on the data file can be defined by another application.
hLockNo No lock: the record can be read or modified by another application.

Remarks

Modifying the type of lock for a record

To modify the type of record lock, call HLockRecNum and specify the requested type of lock. There is no need to unlock the record beforehand.

Effect of lock mode

HLockRecNum has no effect if the lock mode of the data file is set to hModeMono (see HMode).

Lock failure

If the record is already locked, the lock request is retried HNbRetry times (50 by default).

If the data file cannot be locked after H.NbRetry attempts, HErrorLock returns True. The H.Level variable indicates whether the record or the data file is locked.

Number of locks

The number of records that can be individually locked in a data file is unlimited.

Native SQL Server Connector: Lock in write mode

HLockRecNum locks the record in write mode, not in read-only. Therefore, HLockRecNum prevents the record from being modified by another computer.

HLockRecNum used on a locked record does NOT return a lock error (because only a read operation is performed).

However, HModify will return a lock error on the locked record.

Managing locks in OLE DB

HLockRecNum is not supported. This function generates the non-fatal error "Invalid operation for this type of database".

Persistence of lock

With the Native SQLServer and Sybase Connectors, re-reading a record that was locked by HLockRecNum unlocks the record.

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