On MongoS:
- setDefaultRWConcern - passes through to the same command on the config server
 - getDefaultRWConcern - passes through to the same command on the config server by default; if inMemory requested, then returns the locally cached value
 
On Config Server or Plain Replica Set (not a shard):
- setDefaultRWConcern - persists to disk
 - getDefaultRWConcern - by default returns what's persisted on disk; if inMemory requested, then returns the locally cached value
 
On Shards:
- setDefaultRWConcern - should error, because it must never be called directly
 - getDefaultRWConcern - should error, because it must never be called directly
 
- is depended on by
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SERVER-45221 Complete TODO listed in SERVER-43720
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 - Closed
 
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- is duplicated by
 - 
                    
SERVER-43718 Make RWCDefaults persist changes
-         
 - Closed
 
 -         
 
- is related to
 - 
                    
SERVER-45052 Separate out RWCDefault jstests into appropriate suites
-         
 - Closed
 
 -         
 
- related to
 - 
                    
SERVER-45221 Complete TODO listed in SERVER-43720
-         
 - Closed
 
 -