Huge load after update from 2.3.16 to 2.4.12

[plate at bibliothek.uni-kassel.de]

[...]
>
> When performing an upgrade from earlier than 2.4.3, all messages are
> reparsed, and your cache files are re-generated, when a mailbox is first
> opened. You may be able to increase you syslogging levels to get a better
> view into what's going on:
[...]

Thanx,

four weeks ago I made a dump and tried a new installation on a test
machine, but I had no problems.

CU

Michael