Alfresco 4.2 to 51 Upgrade Steps (Windows)
Prerequisites
Take down your running 4.2Coldbackup - Take backup of your contentstore and database (you can gather the info from alfresco-global.properties file from <alfresco-home>/tomcat/shared/classes directory)
Steps to Upgrade
Step 1. Install Alfresco 5.1 using Windows Installer using postgres database
Select the components such as
Java,
PostgreSQL
GoogleDoc association(optional)
Step 2. Apply the custom amps (if you have any), configurations for Alfresco 5.1
update ldap
update alfresco-global
apply license
Add MSSQL/MySQL/Oracle(etc) lib
Step 3. Restart the service
Step 4. Validate the amps and its configuration
Step 5. Bring down the alfresco services and restore it using 4.2 content store & DB backup
Update alfresco-global - alf_data location/ to old
Update (old)database info
Step 6. Restart the alfresco instances and sanity check (solr indexing, share)