Does Sharepoint Differential backup put the site collection in read only mode?
Actually, that's going to depend on what release and build version of SharePoint you're using.
- If you have a SharePoint 2007 farm that hasn't yet been patched to Service Pack 2, you're going to have to manually lock the site collection before you back it up, regardless of whether its a Full or Differential backup. (And for goodness sakes, please patch it up to Service Pack 2 and the latest Cumulative Update as soon as you can!) This blog post has a nice writeup of what was introduced in Service Pack 2: http://sharepointblog.michaelrperry.com/2009/06/stsadm-backups-with-service-pack-2.html
- But if you have at least Service Pack 2 of MOSS 2007 or SharePoint 2010, SharePoint will now automatically lock the targeted item before backing it up and then unlock it once the backup is completed. If you don't want to lock the site, use the -NoSiteLock switch in your call to Backup-SPSite (this works w/ SharePoint 2010, not sure if there is an equivalent option w/ SharePoint 2007 or not)
I don't think it was intentional, but this is actually something of a trick question. Let me explain.
There are basically two different types of backups that you can perform: farm-level (catastrophic) backups and site collection backups. The former is used to back up components such as the entire farm, a Web application, a content database, etc. The latter, on the other hand, is used to back up an individual site collection. Each backup type is implemented and conducted differently within the SharePoint Object Model.
To help tell them apart:
- Farm-level backup:
STSADM.exe -o backup -directory <UNC path>or
- Site collection backup:
STSADM.exe -o backup -url <URL>or
So, here's the tricky part: full-farm backups can be carried out in full or differential mode, but site collection backups can only be carried out as a full backup. There actually isn't any "differential site collection" backup using out-of-the-box tools.
John Ferringer's answer is absolutely correct for site collection backups, but I'm guessing that you were probably asking whether or not your site collections (any of them) would become locked (i.e., placed in read-only mode) if you were to carry out a differential farm-level backup that included content databases where site collections are housed. The answer in that case is "no." Those backups are not handled in the same was as site collection backups, and so there isn't the same need to lock site collections.