Locks a record and restricts the access to this record for all the other applications. Then, the record can be unlocked by
HUnlockRecNum.
Note: 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.
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.
Versions 16 and later
New in version 16Versions 17 and later New in version 17 Versions 18 and later New in version 18 Versions 21 and later New in version 21 Note: From version 19, HFSQL is the new name of HyperFileSQL.
// Lock a record found in CUSTOMER file
HLockRecNum(CUSTOMER, hCurrentRecNum, hLockReadWrite)
// Process on the record
...
// Give the access back to the record
HUnlockRecNum()
Syntax
<Result> = HLockRecNum([<File Name> [, <Record Number>]] [, <Lock>])
<Result>: Boolean
- True if the operation was performed,
- False if a problem occurred. HError is used to identify the error.
<File Name>: Optional character string (with or without quotes)
Name of data file used. If this name is not specified, HLockRecNum handles the last data file used by the last function for HFSQL management (starting with the letter H).
<Record Number>: Optional integer
Number of the record to lock. If this parameter is not specified, HLockRecNum handles the current record.
<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.
HLockRecNum has no effect if the lock mode of data file is set to
hModeMono (see
HMode).
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.
The number of records that can be individually locked in a data file is unlimited.