XMLDataSource error in Kentico 9 site

I would check the XML data source setup - on what page it is and what data it is pulling. Maybe it is pulling too much data from the DB and it takes long time so it times out. There must have been done some changes...

thanks looks like the db data file space is pretty much fool, it's 105GB now. Will increase data file space help? what's the recommended db size? sorry our DBA quit we don't have a DBA now

That is a pretty big DB. There are no recommendations as this vary per project. IF you have big newspaper web site then the size is OK. But if it is a small company web, it is not OK and something is wrong. I would recommend reviewing the backup and transaction log settings, use Google to see how to reduce the DB size, shrink it etc.

by checking the disk usage report, I found that the tables Staging_Task, CMS_ObjectVersionHistory, CMS_Attachment,and all the Analytics_xxxhits talbes are the top tables. And I noticed that the task Remove analytics data is disabled.

So, you should do some cleanup in the admin UI and delete the unused staging tasks, clear up attachments and so on...

thanks, let me check if I can do more cleaning with built in tasks

I didn't find any task to delete unused staging tasks, it's not a builtin task? can I delete from the database directly?

And also no tasks for clean attachment history, object version history either

Well, maybe those are orphaned tasks from some deleted staging server. The same for the other - this indicates some inconsistency in the DB and you should be cautious. While you can delete the staging tasks directly, for the version history records I would recommend something like this

thank you again for your help!