Standard sync, optimized for speed by bypassing any unneeded steps.
Sync even if the upstream metadata appears to have no change. This option is only relevant for yum repositories and will take longer than an optimized sync. Choose this option if:
Performs a complete sync, verifying the checksum of all packages afterwards. Any missing or corrupt package will be re-downloaded. This option will take the longest amount of time. Choose this option if: When validating content, repositories using the "On Demand" download policy will download all packages within the repository.