Open Query File
1. What is an Open
Query File?
Open query file is a dynamic
selection of records. It retrieves records thro’ open data path. So it’s
processing time is slow.
Functions supplied by OPNQRYF are:
§ Dynamic
keyed sequence access path
§ Dynamic
keyed sequence access path over a join.
§ Dynamic
join
§ Handling
missing records in secondary join files
§ Unique-key
processing
§ Mapped
field definitions
§ Group
processing
2. What does the Open Query file do?
Creates an open
data path to physical file data.
3. Notify the wrong steps in the
following.
a. OVRDBF b.
OPNQRYF c. OVRDBF d . OPNQRYF
OPNQRYF
OVRDBF OPNQRYF OVRDBF
CALL PGM
CALL PGM CALL PGM CALL PGM
CLOF DLTOVR DLTOVR CLOF
DLTOVR CLOF CLOF DLTOVR
a and b are correct steps.
4. What are the
various steps involve creating an Open Query File? (Or) What are the mandatory
steps for Open Query File?
OVRDBF
If a physical file having 100
records and if we want to override the PF. So that it contains only the
specific number of records we are using OVRDBF
OPNQRYF
If you want to perform a SQL
operation, we have to declare in OPNQRYF command only.
OPNQRYF (FILE PF) QRYSLT (‘EMPNO *EQ’ *BCAT &A) will retrieve empno equals &A QRYSLT (‘EMPNAME *EQ % WLDCRD (“S*”)’) will retrieve empname which starting with s QRYSLT (‘EMPNAME *CT “S”’) will retrieve empname contain SQRYSLT (‘EMPNO *EQ% RANGE
OPNQRYF (FILE PF) QRYSLT (‘EMPNO *EQ’ *BCAT &A) will retrieve empno equals &A QRYSLT (‘EMPNAME *EQ % WLDCRD (“S*”)’) will retrieve empname which starting with s QRYSLT (‘EMPNAME *CT “S”’) will retrieve empname contain SQRYSLT (‘EMPNO *EQ
CALL / PROCESSING/CPYFRMQRYF
To see the records being selected
we have to copy from the source file to a temporary file for this action
CPYFRMQRYF will be used.
DLTOVR
As we see early the main file is logically
overridden and after performing the necessary operation, we have to delete the
logical file. So that the main file contain the actual records. For this action
DLTOVR will be used
CLOF
Finally
we have to close the file, which is opened.
5. What do you mean by Open data path?
It is an
imaginary pointer and it will move from one record to another while the file is
being read.
6. How to share the ODP?
By using OVRDBF
command and make sure of the parameter SHARE (*YES).
7. What is the purpose of OVRDBF
SHARE (*YES)?
By sharing the
path *YES, the data is passed to the subsequent usage of that file, until the
override is deleted.
8. What is the main purpose of overriding any file?
This command is
mainly used to override the file’s attribute(s).
9. Override DBF - Explain.
It is used to
share the open data path.
It is used to
redirect the file name.
It used over the file by its
member.
10. How to use all the members in a P.F
Use OVRDBF with
member option *all
11. Is it possible to create a new field dynamically?
Yes. By using
OPNQRYF command you can create a new field dynamically by defining the new
field in MAPFLD parameter.
12. Can we over ride other files apart from DBF?
Yes. We can use
OVRPRTF, OVRDSPF, OVRTAPF, and OVRDKTF
13. What is the purpose of OVRPRTF [Over ride Printer file]?
To change the
no. of copy dynamically, one can use the OVRPRTF command.
14. What is the CPF9899 error?
It is the CL
program message ID for Open query file error.
15. What are the
advantages for using Open Query File?
·
Dynamic selection of records.
·
Can create a join logical file.
·
Dynamic join.
·
Virtual field can be used.
·
Accessing by open data path
·
Group processing
[Virtual field does not exist in
PF. But it is the combination of PF fields. Let PF01 has empno, salary, allow.
and OpnQryF has empno, net=salary+allow. Here net is virtual field]
16. How are the
records accessed in Open Query File?
By
creating an Open Data Path, it will access the records from the PF/LF.
17. What are the
differences between SQLRPG, Open query File and Logical File?
Open query file
|
Logical file
|
SQLRPG
|
1. Selection is throgh’ Open Data Path
2. Dynamic selection
3. Slow process
4. Virtual field can be used
5. Dynamic join
6. We can use more selection criteria
|
1. Selection is thro’
Access Path.
2. Static selection
3. Fast process
4. Can not be used
5. Static join
6. Can not use more selection criteria
|
1. Selection thro’ Access path
2. Dynamic selection
3. Slow than OPNQRYF
4. Can not be used.
5. Dynamic join.
6. Can use more selection criteria.
|
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