备份数据库在SQ8.4版本，恢复在8.3版本时报错：Database was upgraded to a more recent version of SonarQube. A backup must probably be restored or the DB settings are incorrect.

如果版本不一致，可能涉及到升级问题，查看sonar.log即可

...
2020.10.21 11:14:27 ERROR web[][o.s.s.p.PlatformImpl] Web server startup failed: Database was upgraded to a more recent version of SonarQube. A backup must probably be restored or the DB settings are incorrect.
2020.10.21 11:14:27 INFO  web[][o.s.s.a.EmbeddedTomcat] HTTP connector enabled on port 9000
2020.10.21 11:14:27 INFO  web[][o.s.p.ProcessEntryPoint] Hard stopping process
...

使用相同的SQ，可正常启动——备份恢复成功。

使用SQ8.5版本时，启动后首页提示：

SonarQube is under maintenance

While waiting, you might want to investigate new plugins to extend the current functionality.

If you are an administrator and have no idea why this message is being shown, you should read the upgrade guide.

官方指导upgrade guide.

• 下载、解压
• 根据兼容性列表复制对应的插件到插件目录extensions/plugins
• 更新对应的配置文件sonar.properties 和 wrapper.conf
• 停止旧版本、启动新版本
• 访问http://yourSonarQubeServerURL/setup目录根据提示进行升级操作