Ü
UNLOCK
(Unlock Data
Area/Unlock Record Lock in a file)
I.
Unlock Data Area
·
This opcode is used to unlock
the dataarea.
|
Factor 1
|
Op-code
|
Factor 2
|
Result Field
|
Resulting Indicators
HI LO EQ
|
|
UNLOCK(E)
|
Data area name
|
|
|
Error
|
|
Example
Columns . . . : 6 76 Edit AMINEM/PRJ1
SEU==> GENACC
FMT C CL0N01Factor1+++++++Opcode&ExtFactor2+++++++Result++++++++Len++D+HiLoEq
*************** Beginning of data *************************************
0004.00 C *DTAARA DEFINE DA 12
0005.00 C *ENTRY PLIST
0006.00 C PARM A1 12
0007.00 C *LOCK IN DA
0008.00 C MOVEL DA C 12
0009.00 C MOVEL *ZEROS I 12 0
0010.00 C EVAL I=%INT(C)
0011.00 C ADD 1 I
0012.00 C EVAL C=%CHAR(I)
0013.00 C MOVEL C DA
0015.00 C MOVEL C A1
0016.00 C OUT DA
0017.00 C UNLOCK DA
0019.00 C SETON LR
0020.00 C return
****************** End of data ****************************************
Below
is the dataarea used in the program “DA”:
Display Data Area
System: SYSTEM09
Data area . . . . . . . : DA
Library . . . . . . . : QGPL
Type . . . . . . . . . : *CHAR
Length . . . . . . . . : 30
Text . . . . . . . . . :
Value
Offset *...+....1....+....2....+....3....+....4....+....5
0 '100000000001'
F3=Exit F12=Cancel
OUTPUT
On each call of this program, auto-generation of number will
happen.
The generated number will be updated to the dataarea.
II.
Unlock
Record Lock in a file
§
The UNLOCK operation makes the current locked record to be
unlocked for an update operation on a file.
§
The current locked is unlocked on subsequent read operation
i.e. when we read another record the previous read operation record lock will
be unlocked.
§ The current locked record is
automatically unlocked when the UPDATE operation performed on the record is
over.
Example
§ There is one physical file MASTER with
the record as below:
ORG CODE ACC NUMBER CURRENCY OPEN DATE PARTY NUM
191 A00000000002 USD 20120605 P00000000002
191 A00000000004 EUR 1072012 P00000000004
191 A00000000005 USD 6072011 P00000000005
192 A00000000006 USD 9082012 P00000000006
191 A00000000007 EUR 9082000 P00000000007
191 A00000000008 USD 9082007 P00000000008
192 A00000000009 TRY 6092000 P00000000009
§ We have created 2 programs OP_UPDATE1
& OP_UPDATE2.
Columns . . . : 6 80 Edit AMINEM/QRPGLESRC
SEU==> OP_UPDATE1
FMT H HKeywords++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
*************** Beginning of data ****************************************************
0001.00 HOPTION(*NODEBUGIO) 130131
0002.00 FMASTER UF A E K DISK USROPN 130130
0009.00 * 130124
0010.00 C OPEN MASTER 130130
0011.00 C *LOVAL SETLL REC1 130131
0012.00 C READ MASTER 130131
0013.00 C DOW NOT %EOF(MASTER) 130131
0014.00 C IF ACC='A00000000002' 130131
0015.00 C EVAL CCY='USD' 130131
0016.00 C UPDATE REC1 130130
0017.00 C ELSE 130131
0018.00 C UNLOCK MASTER 130131
0019.00 C ENDIF 130131
0020.00 C READ MASTER 130131
0021.00 C ENDDO 130131
0023.00 * 130123
0024.00 C SETON LR 130123
****************** End of data *******************************************************
Columns . . . : 6 80 Edit AMINEM/QRPGLESRC
SEU==> OP_UPDATE2
FMT H HKeywords++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
*************** Beginning of data ****************************************************
0001.00 HOPTION(*NODEBUGIO) 130131
0002.00 FMASTER UF A E K DISK USROPN 130130
0003.00 130121
0004.00 C OPEN MASTER 130130
0005.00 C *LOVAL SETLL REC1 130131
0006.00 C READ MASTER 130131
0007.00 C DOW NOT %EOF(MASTER) 130131
0008.00 C IF CCY='EUR' 130131
0009.00 C EVAL ACCSTS=4 130131
0010.00 C UPDATE REC1 130130
0013.00 C ENDIF 130131
0014.00 C READ MASTER 130131
0015.00 C ENDDO 130131
0016.00 130131
0017.00 C SETON LR 130123
****************** End of data *******************************************************
§ Here both the programs are trying to
update the same file. Suppose the first program has read one record from the
physical file ‘MASTER’.
§ There will be lock on the file once is
READ operation is performed on the file and the lock won’t be released until
any other READ or UPDATE or UNLOCK is performed.
§ Now 2nd program tries to
access the same record to update it. But it gets an error message “Unable to allocate a record in file
MASTER” since that record is
allocated to the first program.
§ Here 2nd program has to wait
for the 1st program to release the lock on that record.
§ To release the lock 1st
program uses UNLOCK if the record it has read is of no relevance.