Eon Mode only

Sets the strategy the optimizer uses when splitting responsibility for professing data in a shard among the shard's subscribers. This hint only has an effect if the subcluster is using ECS, which is the case when the subcluster contains more nodes than there are shards in the database. See Manually Choosing an ECS Strategy for details.


SELECT /*+ ECSMODE(option)*/ ...



Specifies the strategy to use when splitting data in a shard among its subscribing nodes:

  • AUTO—tells the optimizer to determine the strategy to use automatically. Only useful if you have set the ECS mode at the session level (see Setting the ECS Strategy for the Session or Database).
  • COMPUTE_OPTIMIZED—Force the use of the compute-optimized strategy.
  • IO_OPTIMIZED—force the use of the I/O-optimized strategy.
  • NONE—disable the use of ECS for this query. Only the participating nodes will take part in the query. The collaborating nodes will not take part.


The following example shows the query plan for a simple single-table query that is forced to use the compute-optimized strategy:

=> EXPLAIN SELECT /*+ECSMode(COMPUTE_OPTIMIZED)*/ employee_last_name,
             FROM employee_dimension 
             ORDER BY employee_age DESC;

                                   QUERY PLAN 
 The execution of this query involves non-participating nodes.  
 Crunch scaling strategy preserves data segmentation
. . .