I've spent the last couple of months helping a customer migrate a large Portal 126.96.36.199 environment to Portal 188.8.131.52.
This customer was somewhat unique in that they made extensive use of the WMM lookaside database in 6.0. All this lookaside data needed to correctly migrated to VMM (a.k.a WIM) in Portal/WAS 6.1. The volume of data in the WMM lookaside database was rather large and the customer knew, going in, that this would like be a source of risk during the migration.
As it turns out, the volume of data in the lookaside combined with the fact that the database was Oracle (10g) exposed several issues in the code designed to copy the WMM data to VMM during the migration.
Prior to the migration, the customer upgraded the 184.108.40.206 Portal to 220.127.116.11. This was required to pick up the Portal/WAS migration prereq APARs required for migration. The target environment was installed and upgrade to Portal 18.104.22.168 running on WAS 22.214.171.124. Again this took us to the known and required levels of Portal and WAS for a migration.
Before it was all over, we required the following Portal and WAS APARs in order to successfully migrate the WMM to VMM data:
The first 4 are WAS APARs, the last on is a Portal APAR