RE: Change spooled file attribute...

This is a logic scheme:

1. Retrieve Spooled File Attributes (QUSRSPLA) API - returns specific
information about a spooled file into a receiver variable. Use
'SPLA0200' format.
2. Change USRDFNDTA in returned receiver (or other important
parameters).
3. Create User Space (QUSCRTUS) API - creates a user space. You need it
to use next API's.
4. Open Spooled File (QSPOPNSP) API - opens an existing spooled file.
5. Get Spooled File Data (QSPGETSP) API - gets data from an existing
spooled file and store in a user space (previously created). Use
'SPFR0200' format.
6. Close Spooled File (QSPCLOSP) API - closes a spooled file (opened
previously).
7. Create Spooled File (QSPCRTSP) API - create a new spooled file with
attributes based on values taken from 
the spooled file attributes parameter (from receiver - pkt.2).
8. Put Spooled File Data (QSPPUTSP) API - puts data into a spooled file,
which was created using the Create Spooled File 
(QSPCRTSP) API.  The data put in the spooled file is taken from a user
space (stored previously - pkt.5).
9. Close Spooled File (QSPCLOSP) API - close new spooled file.

As a matter of fact as a result You have a new spool file. That's all.
But be careful - some API's (like QSPCRTSP) need high authority.

P.S.

Sorry for my English. It's still foreign language for my ;^)

regards

Wojciech Gwiazdowski