You've seen lock operations; GETATTR operations are simply file operations that examine the attributes of a file (who owns it, what time it was last modified, and so forth[17]). Lock and GETATTR operations require the NFS client to communicate with the NAS server using the get attribute or GETATTR call of the NFS protocol. This brings us to the topic of attribute caching— a method you can use to improve the performance of GETATTR calls.
[17]All inode information about the file.