I have a pile of SQL 2005 databases that have been around for a very long time and, for varying reasons, experienced transaction log autogrowth. Regular backups now keep the transaction log usage under control, but the files are still large and fragmented. 

I'd like to reclaim some of that space and boost performance by reducing the number of VLFs. However, I'd also prefer not to disrupt our scheduled backups. How does DBCC SHRINKFILE() affect the transaction log backup chain? Or does it? Does this change if I add TRUNCATEONLY to the command?

*Note that this is a one-time fix. I'm well aware that regularly shrinking logfiles is a Bad Thing - had these databases been configured with rational initial sizes and autogrowth settings and had backups run perfectly every day of their history, this would not be an issue.*