Portal | Manuals | References | Downloads | Info | Programs | JCLs | Master the Mainframes
IBM Mainframe Computers Forums Index
 
Register
 
IBM Mainframe Computers Forums Index Mainframe: Search IBM Mainframe Forum: FAQ Memberlist Usergroups Profile Log in to check your private messages Log in
 

 

Diff between FB & VB record formats

 
Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> JCL & VSAM
View previous topic :: :: View next topic  
Author Message
isam777

New User


Joined: 27 Jun 2007
Posts: 2
Location: Chennai

PostPosted: Sun Jan 27, 2008 11:57 pm    Post subject: Diff between FB & VB record formats
Reply with quote

Can anyone let me know the difference between the FB and VB Record formats of datasets

Sam
Back to top
View user's profile Send private message

dick scherrer

Site Director


Joined: 23 Nov 2006
Posts: 19270
Location: Inside the Matrix

PostPosted: Mon Jan 28, 2008 8:30 am    Post subject:
Reply with quote

Hello,

FB records are the same length in a file.

VB records may be different lengths in a file.
Back to top
View user's profile Send private message
HappySrinu

Active User


Joined: 22 Jan 2008
Posts: 195
Location: India

PostPosted: Tue Jan 29, 2008 6:36 pm    Post subject: Re: Diff between FB & VB record formats
Reply with quote

isam777 wrote:
Can anyone let me know the difference between the FB and VB Record formats of datasets

Sam


Hey Sam,
FB - > Fixed Block means the entire file is having max of fixed block record

VB - > Variable Block which you can guess by now
Back to top
View user's profile Send private message
superman

New User


Joined: 28 Mar 2011
Posts: 12
Location: india

PostPosted: Mon Nov 21, 2011 6:21 pm    Post subject: Access to which is faster? VB or FB?
Reply with quote

Accessing data in which file is faster VB or FB?
Back to top
View user's profile Send private message
Bill Woodger

DFSORT Moderator


Joined: 09 Mar 2011
Posts: 7308

PostPosted: Mon Nov 21, 2011 8:45 pm    Post subject: Reply to: Diff between FB & VB record formats
Reply with quote

FB.

Edit: Yoy, when you want to ask a new question, start a new topic. What is your interest in the answer?
Back to top
View user's profile Send private message
expat

Global Moderator


Joined: 14 Mar 2007
Posts: 8593
Location: Back in jolly old England

PostPosted: Mon Nov 21, 2011 8:47 pm    Post subject: Re: Access to which is faster? VB or FB?
Reply with quote

superman wrote:
Accessing data in which file is faster VB or FB?

Huh, it's hardly like you get a choice
Back to top
View user's profile Send private message
Pete Wilson

Active User


Joined: 31 Dec 2009
Posts: 440
Location: London

PostPosted: Thu Nov 24, 2011 10:22 pm    Post subject:
Reply with quote

VB files also have 4 bytes reserved in every block for the Block Descriptor Word (BDW), and 4 bytes for each record for the Record Descriptor Record (RDW)

I've been told by programmers that VB are more efficient when you have variable length records, which makes sense because it's more likely fill a block, but that it's harder to write programs to access them.

Best source of info would be IBM's 'Managing Dataset' manual.
Back to top
View user's profile Send private message
Bill Woodger

DFSORT Moderator


Joined: 09 Mar 2011
Posts: 7308

PostPosted: Thu Nov 24, 2011 11:04 pm    Post subject: Re: Access to which is faster? VB or FB?
Reply with quote

expat wrote:

Huh, it's hardly like you get a choice


I'm with expat on this. If your dataset can contain records of different lengths, then you have to at least have V. VB is going to be more efficient than V. You can't use F or FB, unless you make all the records the same length, which could waste the odd byte or two.

What strikes me as odd is the apparent use of V/VB for records which are the same length as each other. That would have a greater overhead than F/FB, plus waste four bytes per record and a futher four bytes per block.

Is, for a programmer, one "easier" to code than the other? It does seem that more people have trouble reading V files than F files, but that is mainly because they don't find out how to do it before attempting it. I don't think that counts as "difficult".

To write a program reading a V file (or any file) I'd copy the code from another program anyway. Same for an F. Or a DB. Or whatever. Same amount of difficulty for all (asuming the code I copy works....).
Back to top
View user's profile Send private message
don.leahy

Active Member


Joined: 06 Jul 2010
Posts: 647
Location: Whitby, ON, Canada

PostPosted: Thu Nov 24, 2011 11:24 pm    Post subject: Re: Access to which is faster? VB or FB?
Reply with quote

Bill Woodger wrote:
expat wrote:

Huh, it's hardly like you get a choice


What strikes me as odd is the apparent use of V/VB for records which are the same length as each other. That would have a greater overhead than F/FB, plus waste four bytes per record and a futher four bytes per block.


Odd indeed. I have been in a situation when it was necessary. We had to transfer files to another platform, and the application on that side demanded that the records be fixed length. No problem, we copied the file from VB to FB and transmitted it to them. The problem was that the file transfer utility (not FTP, I think it was NFS) "helped" us out by dropping all of the trailing blanks on each record. This was not acceptable to the receiving app, which, for some reason (it was a packaged product) could not handle what was actually a traditional line sequential file with records terminated with CRLF. It needed the CRLF to be in a fixed position for all records.

We couldn't get the file transfer process to handle it for us, so we resorted to creating the file as VB, with all of the records blank padded to the maximum lrecl. We called this "fixed variable" format (that was what we told management, our own name for it was unprintable) and did the trick because the file transfer process would respect the RDW and create the file accordingly.

Sometimes stupid things are done for a reason.
Back to top
View user's profile Send private message
View previous topic :: :: View next topic  
Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> JCL & VSAM All times are GMT + 6 Hours
Page 1 of 1

 

Search our Forum:

Similar Topics
Topic Author Forum Replies Posted
No new posts Record Not found in AlX but record re... mukun264 COBOL Programming 7 Fri Mar 24, 2017 9:28 am
No new posts Count the length of the record & ... sreekusr DFSORT/ICETOOL 4 Thu Mar 23, 2017 7:52 pm
No new posts IMS DB-How to update a record (a sing... Nic Clouston IMS DB/DC 9 Thu Mar 09, 2017 4:38 pm
No new posts To Merge mutliple records into a sing... anandgbe DFSORT/ICETOOL 6 Wed Feb 22, 2017 8:49 am
No new posts How to update a portion of text in a ... Bill Woodger DFSORT/ICETOOL 25 Wed Nov 09, 2016 9:41 pm


Facebook
Back to Top
 
Mainframe Wiki | Forum Rules | Bookmarks | Subscriptions | FAQ | Tutorials | Contact Us