So why the need for registry defrag?
And for portable version do you have to manually run the database updater? i.e install version after install automatically does a database update, what about portable version database update?
The registry defrag is a little different than a disk defrag. Registry data structure is stored in registry hive files. This files are loaded during computer boot into the memory. The more fragmented the registry are, the bigger the registry hives. This mean that the boot time will be bigger. So basically the registry defrag is done to shrink the registry hive files, this leading to a better boot time.
Disk defrag is done to improve seek time when accessing the file. When accessing a file, the more fragmented it is, the longer it will take to read it, because it's buffers are spread all over the HDD. Because the seek time of a SSD is almost 0, the defrag is no longer needed.
In the portable version, a manual database update is needed. We cannot run automated tasks in the portable version ( task schedule, update service ) because this will no longer make the version portable.