This is a count of times the XQP (Extended QIO Processor, the file system's core process) had to wait due to volume lock contention. An administrator watches this counter to detect when multiple processes are contending for exclusive access to the same disk volume, which can slow file operations system-wide. For example, a climbing vmsFcpVolumeLockWait count during heavy multi-user file activity on a shared volume would point to volume-level lock contention as a performance bottleneck.