IBM Mainframe Forum

Hi,

Is it possible to concatenate two different LRECL files ?

I am changing the LRECL of one production FIle...But thing is its a daily job..so till 18th the file ll be created as 178 LRECL, from 19th it ll be created as LRECL 225..During month-end another jb will take Backup of all the files & Concatenate..

Is it possbile to concatenate ? Somewhere i read the we can concatenate ddiff lrecl files,if we code the Bigger BLKSIZE file in the top,

Say,
sortid dd file1225
dd file2178

sortout dd file3225

Is it possbile to concatenate ? Somewhere i read the we can concatenate ddiff lrecl files,if we code the Bigger BLKSIZE file in the top,

As long as the files have variable or variable blocked (RECFM=V or VB) records, you can concatenate files with different LRECLs together.

However, if the files have fixed or fixed blocked (RECFM=F or FB) records, you cannot concatenate them together -- in this case you would need to reformat the shorter records to be the same length as the longer records.

debo wrote:Somewhere i read the we can concatenate ddiff lrecl files,if we code the Bigger BLKSIZE file in the top

I'd like to know where you may have read that from. It's either inaccurate or was taken out of context.

MrSpock wrote:

debo wrote:Somewhere i read the we can concatenate ddiff lrecl files,if we code the Bigger BLKSIZE file in the top

I'd like to know where you may have read that from. It's either inaccurate or was taken out of context.

The rules you can use to concatenate files with differing DCB attributes are pretty arcane. For variable length files, you should be able to concatenate the files pretty easily, provided your program can handle both the shorter and longer LRECLs. For fixed length record data sets with a fixed LRECL, the larger BLKSIZE should be first, or the maximum BLKSIZE should be specified in the JCL. This was always true until one of the OS/390 releases I think it was, when you no longer had to specify the maximum BLKSIZE in the JCL, which was quite convenient when concatenating PDS data sets for somethiing like an Assembler SYSLIB or a PROCLIB. Fixed length data sets with different LRECLs cannot be concatenated unless you have an Assembler program that is written to handle "unlike" concatenation. This is quite difficult, more so than the manual seems to read. I tried it a couple of times, but I can't recall I ever got it to work. There's a chapter about concatenating "unlike" data sets in DFSMS Using Datasets, but the manual is oriented towards us old Assembler programmer dinosaurs, so it may not be useful for either MrSpock or debo. Good luck!

Somewhere i read the we can concatenate ddiff lrecl files

hard to believe, You can concatenate different blcksize datasets as long as ...

1) put first in the concatenation the dataset with the largest blcksize
2) specify on the first DD of the concatenation the largest blksize of the concatenation
( or for dasd datasets simply code the largest multiple of the lrecl that fits in the 32767 blksize limit )

the reason is that MVS will allocate buffers for I/O based on the blksize of the first dd in the concatenation

During month-end another jb will take Backup of all the files & Concatenate..

Sounds to me as though your backup process was implemented without much forthought

http://www.geekinterview.com/question_details/59459

Please refer the above link..But i think if Blksize is different we can concatenate..otherwise we cant

Hello,

But i think if Blksize is different we can concatenate..otherwise we cant

Completely incorrect. . . Concatenation is allowed for the same or different block sizes. . . Re-read what Enrico posted.

The posted link is about concatenating different lrecls, not blksizes. . .