as400 interview questions and answers-Part 24
1. Explain READ opcode in rpgle with example.
Ans:
READ (N | E) (Read a Record)
·
Read operation reads the records of
a full procedural file. First of all it reads the record where currently the
pointer is and then advances the pointer to the next record.
·
The READ operation applies a record
lock to files that are open in update mode. To avoid lock we use operator
extender ‘N’.
·
To handle READ exceptions (file
status codes greater than 1000), either the operation code extender 'E' or an
error indicator at LO level can be used.
·
If the data-structure is specified
in result field then the result of the operation is filled in the data structure.
·
If there is an error or there is
end of file condition, then we must reposition the file pointer to a valid
record. For pointer reposition we can use CHAIN, SETLL or SETGT operation.
·
The Equal Indicator gets turned-on
if the EOF condition is met else it will be off. Instead of using this
indicator we can also go for %EOF ().
|
Factor 1
|
Op-code
|
Factor 2
|
Result Field
|
Resulting Indicators
HI LO EQ
|
|
|
READ(N|E)
|
File or record format
name
|
Data structure to hold
the result
|
|
Error
|
End-of-file condition
indicator
|
Example –
I
Columns . . . : 6 80 Browse AMITCC/QRPGLESRC
SEU==> OP_READIND
FMT FX FFilename++IPEASF.....L.....A.Device+.Keywords+++++++++++++++++++++++++++++
*************** Beginning of data ****************************************************
0001.00 FPF0001 IF E K DISK
0002.00 DDS1 DS LIKEREC(REC2)
0003.00 C *LOVAL SETLL REC2
0004.00 C READ PF0001 DS1 90
0005.00 C DOW *IN90=*OFF >>>>>> *in90 at EQ-position indicates
0006.00 C DS1 DSPLY EOF() condition
0007.00 C READ PF0001 DS1 90
0008.00 C ENDDO
0009.00 C IF *IN90=*ON
0010.00 C 'END OF FILE' DSPLY
0011.00 C ENDIF
0012.00 C SETON LR
****************** End of data *******************************************************
Output
AMINEM P00000000001CONIZA TOJ020120121
IROBO P00000000002HENGURIZZA010620121
END OF FILE
Example –
II
Columns . . . : 6 80 Browse AMITCC/QRPGLESRC
SEU==> OP_READIN2
FMT FX FFilename++IPEASF.....L.....A.Device+.Keywords+++++++++++++++++++++++++++++
*************** Beginning of data ********************************************
0001.00 FPF0001 UF A E K DISK
0002.00 DDS1 DS LIKEREC(REC2)
0003.00 C *LOVAL SETLL REC2
0004.00 C READ PF0001 DS1 >>> DS1 = Data structure to store result
0005.00 C DOW NOT %EOF(PF0001) >>>> Using %EOF() instead of EQ
0006.00 C DS1 DSPLY resulting indicator
0007.00 C READ(N) PF0001 DS1
0008.00 C ENDDO
0009.00 C IF %EOF(PF0001)
0010.00 C 'END OF FILE' DSPLY
0011.00 C ENDIF
0012.00 C SETON LR
****************** End of data ************************************************
OUTPUT
AMINEM P00000000001CONIZA TOJ020120121
IROBO P00000000002HENGURIZZA010620121
END OF FILE