JAVA: Read file with IFSFileInputStream, then write to TAPE

Hi Gary,
i can write to streamfile then save the streamfile to tape, but it will occupy large temporary space as the file(s) being processed are big (tens of gigs).

Do you need to write to tape in standard labeled format, or can you write in IBM's Save/Restore format?  If Save/Restore format is OK, then you can just use the CL command SAV (http://publib.boulder.ibm.com/iseries/v5r2/ic2924/index.htm?info/cl/sav.htm) to save the stream file directly to tape.

Using Save/restore format, you'll only be able to restore it on another AS/400, and version restrictions may apply between the two machines.

If the SAV command isn't an option, and the temp space is going to be a problem, then I suppose you could write an RPG (or other native HLL) program that received passed block-sized chunks of data from your Java program and wrote them out to tape a block at a time.  

Of course, if you are going to go to that much trouble, you might as well just write a HLL program to do the whole job: open the stream file, read a block, write to tape file, repeat until done, close tape file, and not fool with the Java-to-Native application-to-application complexities.

This really is one of those tasks that probably lends itself to a native HLL rather than Java.

- Gary Patterson

Gary:

Like you, I've never seen where writing to tape with Java has been needed. But I have a memory of seeing overrides that simply redirected output to QTAPE (or other appropriate tape file). Maybe that's all that's required?

Tom

Tom,

So are you suggesting that the Java program issue the OVRTAPF command, and then write to an overridden database file?  

If so, I don't think SQL will let you override to a non-database file (confirmed - just tried using OVRPRTF and a STRSQL INSERT - SQL7011 - FILE01 in *LIBL not table, view, or physical file.)

That failing, I considered AS400 Toolbox for Java Record Level Access.  

Problem I see here here is that the Java Toolbox RLA classes hand off work like this to a DDM server job.  If the IO is performed out-of-process, the override will not be in effect, so I think that may be a deal-killer.

I think this is a job most easily accomplished with C, C++, RPG, or COBOL.

- Gary Patterson

Gary:

Not exactly OVRTAPF... My (very) foggy memory is more like a way to redirect output to /qsys.lib/somelib.lib/sometapf.file...

Device files are IFS objects after all, and the system knows what methods work with them.

If I can track down explicit references, maybe I'll have more available. I was mostly hoping that you'd seen something similar and I could spark an idea from you. If nothing comes out of it, nothing's lost. But maybe...?

Tom

Hi Gary, Tom,
Thanks for your comments.
I havetried to write directly with java toolbox's IFSFileOutputStream to either /QSYS.LIB/TAP01.DEVD or to /QSYS.LIB/LIBRARY.LIB/TAPEFILE.FILE both return exception, unsuccessful...
Hoping that there's some class somewhere for writing to tape

Writing to the DEVD won't work.  I thought that there was a chance that writing to a properly-configured tape file might.  What exception do you get when you write to the tape file?

- Gary Patterson

Tom,

Now that you've mentioned it, it sounds familiar to me because you can write a binary stream to a tape file in AS400 C/C++.  Never tried it in Java.  Once you mentioned it, though, I was a bit surprised when it didn't work.

I did a bit of reading, and it looks like tape support is notoriously lacking in Java, and not just on AS400.

- Gary Patterson

hmm... if there's a way to write in C/CPP, then there's a chance... the java can 'call' the service program... problem is... i don't know C... i'll be very grateful if you can point me to right direction where to start...

Do you have the AS400 C/C++ compiler?  Most shops don't.  It isn't bundled with the OS, and it isn't free.  

By FAR the most common compiler is RPG, and you can call ILE RPG programs from Java just like you can C/CPP programs.

I probably have an RPG example laying around, but I know I don't have any tape IO in C - might be able to find it on the internet, but like I said, C is not a popular compiler on AS400.

- Gary Patterson

yes i do have c compiler.

Note that all IBM compilers in version 5 of OS/400 are available if any one is licensed, i.e., WDS is licensed. So, if RPG is there, any of the others can be installed (if not already) at no added cost. But it's probably easier in RPG or COBOL than C anyway. It's been maybe 15 years since I did any programmed tape I/O. I'm pretty sure I have no examples.

Regardless, maybe it's time to step back and find out what the actual business requirement is here.

Tom

I just re-read earlier posts -- large intermediate storage spaces are being avoided by going to tape rather than to intermediate disk.

Tom

thanks Gary, I'll take a look

Any luck?

- Gary