Times for conversions (V5R4 to IBM i 7.1 upgrade)
The conversions on your system can have a significant effect on the amount of time required before the upgrade and during normal operations after you upgrade.
For V5R4 to IBM® i
7.1 upgrades, unique
conversions will occur with programs in libraries, Java™ programs in directories, spooled files,
and integrated file system names in file systems that are not case
sensitive. 
Some conversions might have a significant performance
effect when program objects are not converted until accessing the
program for the first time after an upgrade. To make your conversions
run as smoothly as possible, follow the recommendations in the IBM Redpaper publication IBM i Program
Conversion: Getting Ready for IBM i V6R1 
.
More conversions occur if you are skipping
a release level. You need to consider the time for conversions in
both the release you are skipping and in the new release. To estimate
the additional time that conversions might require, you can gather information
about specific object types on your system. To review conversion information
from a skipped release, see the software upgrade information in the IBM i
Information Center 
for
that release.