https://library.netapp.com/ecmdocs/ECMP1196979/html/man5/na_snapmirror.conf.5.html

Each relationship entry of the /etc/snapmirror.conf file is a single line containing space-separated fields.

The entry has this format:

Source destination arguments schedule schedule

This is the schedule used by the destination node for updating the mirror. It informs the SnapMirror scheduler when transfers will be initiated. The schedule field can contain the word sync to specify fully synchronous mirroring, semi-sync to specify semi-synchronous mirroring, or a cron-style specification of when to update the mirror.

visibility_interval

The value for this argument is a number optionally followed by the suffixes: s (seconds), m (minutes) or h (hours). If a suffix is not specified, value is interpreted as seconds. This argument controls the amount of time before an automatic snapshot is created on the source volume that is synchronously mirrored. The value is the number of seconds between automatically created snapshots. The default value is 3 minutes. A small number here can negatively affect the performance of the mirror. This argument is ignored for asynchronous mirrors.

Outstanding (deprecated)

This argument controls the performance versus synchronicity trade-off for synchronous mirrors. The value for this argument is a number followed by the suffixes: ops (operations), ms (milliseconds) or s (seconds). Setting a value less than 10s configures the mirror to run in fully synchronous mode. Setting a value greater than or equal to 10s configures the mirror to run in semi-synchronous mode. This argument is ignored for asynchronous mirrors. Please note that this is a deprecated option. Use the schedule field to specify the synchronous mode for the mirror.

cksum

This controls which checksum algorithm is used to protect the data transmitted by SnapMirror. Currently supported values are "none", "crc32c", and "crc32c_header_only". The value "crc32c_header_only" has been added only for volume SnapMirror and is not supported for synchronous SnapMirror and qtree SnapMirror.