Specifies the shard key for this class.
Until sharded classes are fully implemented, InterSystems recommends creating sharded tables from SQL, not from the object side. However, if you look at a class generated by creating a sharded table, you may see code such as the following:
/// ShardKey index for Sharded table, auto-generated by DDL CREATE TABLE statement
Index ShardKey On DeptNum [ Abstract, CoshardWith = User.Department, ShardKey, SqlName = %ShardKey ];
In this example, the DeptNum property is the shard key of the current class.