Documentation Request Summary:

This patch restricts readConcern level 'snapshot' for use only within multi-statement transactions. Single-statement transactions may no longer specify snapshot readConcern level.

(Note that the above only applies when 'enableTestCommands' has not been set to true. We are allowing in tests for the moment while we convert our snapshot read tests to use multi-statement transactions.)

Engineering Ticket Description:

Snapshot reads outside of multi-statement transactions will be allowed only when enabled via server parameter for testing purposes.