chuawenching, migration from 3.4d to 4.0 working very well !
I have just migrate my 3.4d to 4.0 (keeping mysql database).
This is the way :
1. I'm running Windows 2008 with MySQL. My 3.4 installation rested in "Alfresco" folder, and used "alfresco" database.
2. I shut down old alfresco service and made backups of whole Alfresco folder and (more important in my case) exported current 'alfresco' database.
3. I created a new database (scheme) in mysql: alfresco4 and granted appropriate (mysql) user permissions.
4. I installed Alfresco 4.0.d from setup wizard, into a different folder on disk ("Alfresco4" instead of previous "Alfresco").
a) I selected not to install pgsql.
b) for DB Driver, I entered "org.gjt.mm.mysql.Driver"; for DB URL, I entered "jdbc:mysql://localhost/alfresco4".
5. I copied "mysql-connector-java-5.1.13-bin.jar" file from old installation to new installation.
Path: [alfresco folder]\tomcat\lib\
6. I verified that the service starts and that I could log in with default username "admin" and password. It worked. I stopped the service.
7. I deleted the alfresco4 database and created it anew.
(Or, you could just delete all the individual tables therein… but may encounter some dependency issues.)
8. I imported the database backup (dump) from (2) above into "alfresco4" database.
9. I (after making a backup copy) merged old "alf_data" folder into newly created "alf_data" folder (in "Alfresco4").
10. I started the service and tried to access Alfresco Share and Explorer on their usual addresses. Apparently, engine run all the necessary upgrade tasks. Things seem to work!
11. I switched from "solr" to "lucene" indexing engine. Search now works.
index.subsystem.name=lucene