dbUnlock()

DBUNLOCK()

Unlock a record or release a file lock

Syntax

      DBUNLOCK()

Description

This function releases the file or record lock in the currently selected or aliased work area. It will not unlock an associated lock in a related databases.

Examples

      nId := 10
      USE testid INDEX testid NEW
      IF testid->( DBSEEK( nId ) )
         IF testid->( RLOCK() )
            DBDELETE()
         ELSE
            DBUNLOCK()
         ENDIF
      ENDIF
      USE

Compliance

Clipper

Files

Library is rdd

Seealso

DBUNLOCKALL(), FLOCK(), RLOCK()

dbRUnlock()

DBRUNLOCK()

Unlocks a record based on its identifier

Syntax

      DBRUNLOCK([<xIdentity>])

Arguments

<xIdentity> Record identifier, typically a record number

Description

This function will attempt to unlock the record specified as <xIdentity>, which in a .dbf format is the record number. If not specified, them the current active record/data item will be unlocked

Examples

      PROCEDURE Main()
         USE tests NEW
         DBGOTO( 10 )
         IF RLOCK()
            ? tests->ID
            DBRUNLOCK()
         ENDIF
         USE
         RETURN

Compliance

Clipper

Files

Library is rdd

Seealso

RLOCK(), DBRLOCK(), DBRLOCKLIST()

dbRLockList()

DBRLOCKLIST()

This function return a list of locked records in the database work area

Syntax

      DBRLOCKLIST() --> aRecordLocks

Returns

<aRecordList> is an array of lock records

Description

This function will return an array of locked records in a given and active work area. If the return array is an empty array (meaning no elements in it), then there are no locked records in that work area.

Examples

      PROCEDURE Main()
         LOCAL aList := {}
         LOCAL x := 0
         USE tests NEW
         DBGOTO( 10 )
         RLOCK()
         DBGOTO( 100 )
         RLOCK()
         aList := DBRLOCKLIST()
         FOR x := 1 TO Len( aList )
            ? aList[ x ]
         NEXT
         USE
         RETURN

Compliance

Clipper

Files

Library is rdd

Seealso

RLOCK(), DBRLOCK(), DBRUNLOCK()

dbRLock()

DBRLOCK()

This function locks the record based on identity

Syntax

      DBRLOCK([<xIdentity>]) --> lSuccess

Arguments

<xIdentity> Record identifier

Returns

DBRLOCK() returns a logical true (.T.) if lock was successful

Description

This function attempts to lock a record which is identified by <xIdentity> in the active data set. If the lock is successful the function will return a logical true (.T.) value; otherwise a logical false (.F.) will be returned. If <xIdentity> is not passed it will be assumed to lock the current active record/data item.

Examples

      PROCEDURE Main()
         LOCAL x := 0
         USE tests NEW
         FOR x := 1 TO reccount()
            IF ! DBRLOCK()
               DBUNLOCK()
            ENDIF
         NEXT
         USE

Compliance

Clipper

Files

Library is rdd

Seealso

DBUNLOCK(), DBUNLOCKALL(), FLOCK(), RLOCK()

C5_RLOCK

 RLOCK()
 Lock the current record in the active work area
------------------------------------------------------------------------------
 Syntax

     RLOCK() --> lSuccess

 Returns

     RLOCK() returns true (.T.) if the record lock is obtained; otherwise, it
     returns false (.F.).

 Description

     RLOCK() is a network function that locks the current record, preventing
     other users from updating the record until the lock is released.
     RLOCK() provides a shared lock, allowing other users read-only access to
     the locked record while allowing only the current user to modify it.  A
     record lock remains until another record is locked, an UNLOCK is
     executed, the current database file is closed, or an FLOCK() is obtained
     on the current database file.

     For each invocation of RLOCK(), there is one attempt to lock the current
     record, and the result is returned as a logical value.  An attempt to
     obtain a record lock fails if another user currently has a file or
     record lock on that particular record, or EXCLUSIVE USE of the database
     file.  An attempt to RLOCK() in an empty database returns true (.T.).

     By default, RLOCK() operates on the currently selected work area.  It
     will operate on an unselected work area if you specify it as part of an
     aliased expression (see example below).  This feature is useful since
     RLOCK() does not automatically attempt a record lock for related files.

     As a general rule, RLOCK() operates solely on the current record.  This
     includes the following commands:

     .  @...GET

     .  DELETE (single record)

     .  RECALL (single record)

     .  REPLACE (single record)

     Refer to the "Network Programming" chapter in the Programming and
     Utilities Guide for more information.

 Notes

     .  SET RELATION: Clipper does not automatically lock all
        records in the relation chain when you lock the current work area
        record.  Also, an UNLOCK has no effect on related work areas.

 Examples

     .  This example deletes a record in a network environment, using
        RLOCK():

        USE Customer INDEX CustName SHARED NEW
        SEEK "Smith"
        IF FOUND()
           IF RLOCK()
              DELETE
              ? "Smith deleted"
           ELSE
              ? "Record in use by another"
           ENDIF
        ELSE
           ? "Smith not in Customer file"
        ENDIF
        CLOSE

     .  This example specifies RLOCK() as an aliased expression to
        lock a record in an unselected work area:

        USE Sales SHARED NEW
        USE Customer SHARED NEW
        //
        IF !Sales->(RLOCK())
           ? "The current Sales record is in use by another"
        ENDIF

 Files   Library is CLIPPER.LIB.

See Also: APPEND BLANK SET EXCLUSIVE* UNLOCK USE

 

Clipper and Networking

Clipper and Networking

C5 Networking Commands and Functions

DBUNLOCK() :

Release all locks for the current workarea

DBUNLOCK() --> NIL

DBUNLOCKALL() :

Release all locks for all workareas

DBUNLOCKALL() --> NIL

FLOCK() :

Lock an open and shared database file

FLOCK() --> lSuccess

NETERR() :

Determine if a network command has failed

NETERR([<lNewError>]) --> lError

NETNAME() :

Return the current workstation identification

NETNAME() --> cWorkstationName

RLOCK() :

Lock the current record in the active work area

RLOCK() --> lSuccess

SET EXCLUSIVE

Establish shared or exclusive USE of database files

SET EXCLUSIVE ON | off | <xlToggle>

UNLOCK :

Release file record locks set by the current user

UNLOCK [ALL]

C5 Database Functions

AFIELDS() :

Fill arrays with the structure of the current database file

AFIELDS([<aFieldNames>],
    [<aTypes>],
    [<aWidths>],
    [<aDecimals>]) --> nFields

ALIAS() : 

Return a specified work area alias

ALIAS([<nWorkArea>]) --> cAlias

BOF() : 

Determine when beginning of file is encountered

BOF() --> lBoundary

DBAPPEND() : 

Add a new record

DBAPPEND() --> NIL

DBCLEARFILTER() : 

Clear a filter condition

    DBCLEARFILTER() –> NIL

DBCLEARIND() :  Close all indexes for the current work area

    DBCLEARINDEX() --> NIL

DBCLEARREL() : 

Clear active relations

DBCLEARRELATION() --> NIL

DBCLOSEALL() : 

Close all occupied workareas

DBCLOSEALL() --> NIL

DBCLOSEAREA() : 

Close a workarea

DBCLOSEAREA() --> NIL

DBCOMMIT() : 

Flush pending updates

DBCOMMIT() --> NIL

DBCOMMITALL() : 

Flush pending updates in all workareas

DBCOMMITALL() --> NIL

DBCREATE() : 

Create a database file from a database structure array

DBCREATE(<cDatabase>, <aStruct> [, <cDriver> ] ) --> NIL

DBCREATEIND() : 

Create an Index

   DBCREATEINDEX(<cIndexName>, <cKeyExpr>,
        [<bKeyExpr>], [<lUnique>]) --> NIL

DBDELETE() : 

Mark a record for deletion

DBDELETE() --> NIL

DBEDIT() : 

        Browse records in a table layout

    DBEDIT([<nTop>], [<nLeft>],
        [<nBottom>], <nRight>],
        [<acColumns>],
        [<cUserFunction>],
        [<acColumnSayPictures> | <cColumnSayPicture>],
        [<acColumnHeaders> | <cColumnHeader>],
        [<acHeadingSeparators> | <cHeadingSeparator>],
        [<acColumnSeparators> | <cColumnSeparator>],
        [<acFootingSeparators> | <cFootingSeparator>],
        [<acColumnFootings> | <cColumnFooting>]) --> NIL

DBEVAL() : 

Evaluate a code block for each record

DBEVAL(<bBlock>,
    [<bForCondition>],
    [<bWhileCondition>],
    [<nNextRecords>],
    [<nRecord>],
    [<lRest>]) --> NIL

DBF()* : 

Return current alias name

DBF() --> cAlias

DBFIELDINFO() : 

Return and optionally change information about a field

   DBFIELDINFO(<nInfoType>,

        <nFieldPos>,
        [<expNewSetting>]) --> uCurrentSetting

DBFILEGET() : 

Insert the contents of a field into a file

     DBFILEGET(<nFieldPos>, <cTargetFile>, <nMode>)
        --> lSuccess

DBFILEPUT() : 

Insert the contents of a file into a field

     DBFILEPUT(<nFieldPos>, <cSourceFile>)
        --> lSuccess

 DBFILTER() : 

Return the current filter expression as a character string

DBFILTER() --> cFilter

DBGOBOTTOM() : 

Move to the last logical record

DBGOBOTTOM() --> NIL

DBGOTO() : 

Move to a particular record

DBGOTO(<nRecordNumber>) --> NIL

DBGOTOP() : 

Move to the first logical record

DBGOTOP() --> NIL

DBINFO() : 

         Return and optionally change database file information

    DBINFO(<nInfoType>, [<expNewSetting>])
        --> uCurrentSetting

DBORDERINFO() :          Return and optionally change information about orders and index files

    DBORDERINFO(<nInfoType>,   [<cIndexFile>],
        [<cOrder> | <nPosition>],
        [<expNewSetting>]) --> uCurrentSetting

DBRECALL() : 

Reinstate a record marked for deletion

DBRECALL() --> NIL

DBRECORDINFO() :

         Return and optionally change information about a record

    DBRECORDINFO(<nInfoType>,
        [<nRecord>],
        [<expNewSetting>]) --> uCurrentSetting

DBREINDEX() :

         Recreate all active indexes for the current work area

    DBREINDEX() --> NIL

DBRELATION() :

Return the linking expression of a specified relation

DBRELATION( <nRelation> ) --> cLinkExp

DBRLOCK() :      

         Lock the record at the current or specified identity

    DBRLOCK([<xIdentity>]) --> lSuccess

DBRLOCKLIST()          Return an array of the current lock list

   DBRLOCKLIST() --> aRecordLocks

DBRSELECT() :

Return the target workarea number of a relation

DBRSELECT( <nRelation> ) --> nWorkArea

DBRUNLOCK()    

          Release all or specified record locks

    DBRUNLOCK([<xIdentity>]) --> NIL

DBSEEK() : 

Search for a key value

DBSEEK(<expKey>, [<lSoftSeek>]) --> lFound

DBSELECTAR() : 

Change the current workarea

DBSELECTAREA(<nArea> | <cAlias>) --> NIL

DBSETDRIVER() : 

Set the default database driver

DBSETDRIVER([<cDriver>]) --> cCurrentDriver

DBSETFILTER() : 

Set a filter condition

DBSETFILTER(<bCondition>, [<cCondition>]) --> NIL

DBSETINDEX()    

         Empty orders from an order bag into the order list

    DBSETINDEX(<cOrderBagName>) --> NIL

DBSETORDER()

Set the controlling order

    DBSETORDER(<nOrderNum>) --> NIL

DBSETRELAT() :

Relate two workareas

DBSETRELATION( <nArea> | <cAlias>, <bExpr>, [<cExpr>]) --> NIL

DBSKIP() : 

Move relative to the current record

DBSKIP([<nRecords>]) --> NIL

DBSTRUCT() : 

Create an array containing the structure of a database file

DBSTRUCT() --> aStruct

DBUNLOCK()

Release all locks for the current work area

    DBUNLOCK() --> NIL

DBUNLOCKALL()

Release all locks for all work areas

    DBUNLOCKALL() --> NIL

DBUSEAREA() : 

Use a database file in a workarea

DBUSEAREA( [<lNewArea>],
    [<cDriver>],
    <cName>,
    [<xcAlias>],
    [<lShared>],
    [<lReadonly>]) --> NIL

DELETED() : 

Return the deleted status of the current record

DELETED() --> lDeleted

EOF() : 

Determine when end of file is encountered

EOF() --> lBoundary

FCOUNT() : 

Return the number of fields in the current (.dbf) file

FCOUNT() --> nFields

FIELD() : 

Return a field name from the current (.dbf) file

    FIELD/FIELD(<nPosition>) --> cFieldName

FIELDBLOCK() :

Return a set-get code block for a field variable

FIELDBLOCK(<cFieldName>) --> bFieldBlock

FIELDGET() : 

Retrieve the value of a field using the ordinal position of the field in the database structure

FIELDGET(<nField>) --> ValueField

FIELDNAME() : 

Return a field name from the current (.dbf) file

FIELDNAME/FIELD(<nPosition>) --> cFieldName

FIELDPOS() : 

Return the position of a field in a workarea

FIELDPOS(<cFieldName>) --> nFieldPos

FIELDPUT() : 

Set the value of a field variable using the ordinal position of the field in the database structure

FIELDPUT(<nField>, <expAssign>) --> ValueAssigned

FIELDWBLOCK() : 

Return a set-get block for a field in a given workarea

FIELDWBLOCK(<cFieldName>, <nWorkArea>) --> bFieldWBlock

FLOCK() : 

Lock an open and shared database file

    FLOCK() –> lSuccess

FOUND() : 

Determine if the previous search operation succeeded

FOUND() --> lSuccess

HEADER() : 

Return the current database file header length

HEADER() --> nBytes

LASTREC() : 

Determine the number of records in the current (.dbf) file

LASTREC() | RECCOUNT()* --> nRecords

LUPDATE() : 

Return the last modification date of a (.dbf) file

LUPDATE() --> dModification

RECCOUNT()* : 

Determine the number of records in the current (.dbf) file

RECCOUNT()* | LASTREC() --> nRecords

RECNO() : 

Return the current record number of a work area

RECNO() --> nRecord

RECSIZE() : 

Determine the record length of a database (.dbf) file

RECSIZE() --> nBytes

RLOCK()

Lock the current record in the active work area

    RLOCK() --> lSuccess

SELECT() : 

Determine the work area number of a specified alias

SELECT([<cAlias>]) --> nWorkArea

USED() : 

Determine if a database file is in USE

USED() --> lDbfOpen