Safari Books Online is a digital library providing on-demand subscription access to thousands of learning resources.
- Create BookmarkCreate Bookmark
- Create Note or TagCreate Note or Tag
- DownloadDownload
- PrintPrint
E. Debugging Locks > Lock Waits at the Server Level
Lock Waits at the Server Level
A lock wait can happen at either the server level or the storage engine level.[229] (Application-level locks could be a problem too, but we’re focusing on MySQL.) Here are the kinds of locks the MySQL server uses:
- Table locks
-
Tables can be locked with explicit read and write locks. There are a couple of variations on these locks, such as local read locks. You can learn about the variations in the
LOCK TABLESsection of the MySQL manual. In addition to these explicit locks, queries acquire implicit locks on tables for their durations. - Global locks
-
There is a single global read lock that can be acquired with
FLUSH TABLES WITH READ LOCKor by settingread_only=1. This conflicts with any table locks.