I believe I know where/why it's going wrong with anything greater than 3390-27. In my test with a 3390-54, the size of the L1TAB needed for 982800 tracks is 30720. Adding the 1024 bytes for the header gives 31744 bytes. CCKDDU64 does not seem to deal with this, when this first record is greater the the lrecl/blksize of 16384, and it looks like the rewrite table gets corrupted.
I did use #MSG to assist in debugging, but could not use too many of them as? it caused base register addressability to fail due to the increase in csect length.
Now looking at how to correct this........
Andrew
