Yum -clean all........is that a bad thing?

[Leopoldo Olmos]

After yum clean all -and 500 files less- I got the following when I try
to yum update again:

[root at dc85d4bc3 leodoc]# yum update
Repository dag already added, not adding again
Repository freshrpms already added, not adding again
Setting up Update Process
Setting up Repos
Cannot open/read repomd.xml file for repository: core
failure: repodata/repomd.xml from core: [Errno 256] No more mirrors to
try.

Yum was working just fine before the clean all was applied.

Did I mess things up?

Leopoldo Olmos