The standard practice with most quota implementations is to mount all file systems and then run a quota check on each one. The quota check reads all the inodes on disk and calculates the usage for each user and group. This can be time consuming, and because the file system is mounted, the usage can change while quotacheck is running.
VxFS does not support a quotacheck command. With VxFS, quota checking is performed automatically, if necessary, at the time quotas are turned on. A quota check is necessary if the file system has changed with respect to the usage information as recorded in the internal quotas file. This happens only if the file system was written with quotas turned off, or if there was structural damage to the file system that required a full file system check.
A quota check generally reads information for each inode on disk and rebuilds the internal quotas file. It is possible that while quotas were not on, quota limits were changed by the system administrator. These changes are stored in the external quotas file. As part of enabling quotas processing, quota limits are read from the external quotas file into the internal quotas file.