Enormous error logs about deleted sub-wiki

I had created a subwiki named sys and deleted it afterward. Now I found there are a lot of logs about it, most of it is about database schemas like:

Caused by: org.postgresql.util.PSQLException: ERROR: schema "sys" does not exist
Caused by: com.xpn.xwiki.store.migration.DataMigrationException: Unable to update schema of wiki [sys]

Could I just ignore them?

Looks like you deleted the database directly on PostgreSQL and the descriptor for this wiki is probably still here.

Look at http://mydomain/xwiki/bin/view/XWiki/XWikiServerSys

Thanks for your reply. I delete the sub-wiki using web-ui and done nothing to the database directly. BTW, the xwiki/bin/view/XWiki/XWikiServerSys

Could you paste the complete error to get more details because right now all I can say is that XWiki is trying to access wiki “sys” so something is referring it.