Virtual tape optimal image catalog entry size(s).

I've got two stream file directories. One is 7.8GB and one is 13.5GB.
(subject to fluctuation). I want to same them to virtual tape and ftp
that data over to another system for processing. I will INZ the volumes
nightly prior to the backup. If I make too many image catalog entries, or
make them too big, then that just increases ftp time unnecessarily. If I
make them too small will it expand them? Today I did a ftp of two large
stream files
Name Size
VRT01 8,459,776K
VRT02 10,241,024K
1,583,382,689 bytes transferred in 174.085 seconds. Transfer rate 9095.459
KB/sec.
10,483,974,305 bytes transferred in 1179.655 seconds. Transfer rate
8887.320 KB/sec.
I did notice one thing, if I initialized them right prior to the ftp the
size changes:
Size of object data in bytes . . . . . : 12369
Allocated size of object . . . . . . . : 8662810624
Size of object data in bytes . . . . . : 12369
Allocated size of object . . . . . . . : 10486808576
and I resend these I get:
12369 bytes transferred in 0.000 seconds. Transfer rate 0.000 KB/sec.
12369 bytes transferred in 0.000 seconds. Transfer rate 0.000 KB/sec.
So, if I initialize them prior to backup, it will then only have that
nights size. Not sure about an unitialized overwrite.
On the receiving system
Size of object data in bytes . . . . . : 12369
Allocated size of object . . . . . . . : 32768
for both.


Rob Berendt