[-1, 0 - maxagents]
For partitioned database environments and environments in which intra_parallel is set to "Yes", the default is maxagents - num_initagents; otherwise, the default is maxagents. This ensures that, in non-partitioned database environments, max_coordagents always equals maxagents, unless the system is configured for intra-partition parallelism.
If you do not have a partitioned database environment, and have not enabled the intra_parallel parameter, max_coordagents must equal maxagents.
This parameter determines the maximum number of coordinating agents that can exist at one time on a server in a partitioned or non-partitioned database environment.
One coordinating agent is acquired for each local or remote application that connects to a database or attaches to an instance. Requests that require an instance attachment include CREATE DATABASE, DROP DATABASE, and Database System Monitor commands.