See https://docs.sonarqube.org/display/SONAR/Documentation for current functionality
Millions of Violations
If your SonarQube instance contains a lot of coding rule violations, the migration process can take very long (up to a few days).
Therefore, it is highly recommended to directly migrate to version 3.7.2 that speeds up this migration process.
Information provided by the Update Center is erroneous while upgrading from 3.5.X to 3.6
Please rely on the plugin compatibility matrix before upgrading.
There is not such an issue while upgrading from a version prior to 3.5.
Violations and Reviews become Issues
The concept of Violations and Reviews has been merged into a single concept: Issues. Due to this change, some metrics have been removed, others have been added. For example, the 'Unreviewed violations' metric has been removed. If you are using it in some widgets or in alerts, you have to replace it by 'Open issues'.
Migration of the database takes longer than usual
Due to the migration of the concept Violations and Reviews to Issues, the migration of the database takes longer than usual.
Additional memory might be required during the database migration process
During the database migration process, the SonarQube server might require some additional memory.
In SONARQUBE_HOME/conf/wrapper.conf, temporarily increase the value of the