In the shared mode of operation, you can define up to 99 consoles including any subsystem-allocatable consoles for an MVS™ system. In a sysplex, the limit is 99 consoles for the sysplex. You can exceed this number in a system or sysplex by using extended MCS consoles. (See Extended MCS consoles.) Therefore, you should examine any product that uses subsystem-allocatable consoles to determine if it could use extended MCS consoles instead.
In the distributed mode of operation, you can define up to 250 consoles including any subsystem-allocatable consoles for an MVS system. Of these, you can have up to 99 consoles concurrently active on an MVS system. In a sysplex, the limit is determined by the 99 console limit on each MVS system multiplied by the number of MVS systems in the sysplex.
Subsystem allocatable consoles are defined in CONSOLxx and obtained and released using the IEAVG700 interface. Programs invoke IEAVG700 passing in the SCSR (subsystem console service routine) parmlist, which is mapped by IEZVG100. IBM® highly recommends the use of extended MCS (EMCS) consoles rather than subsystem allocatable consoles.
There is no requirement to have an MCS, HMCS or SMCS console configured to each system. You can use command and message routing capabilities on one MCS, HMCS or SMCS console to control multiple systems in the sysplex. MCS, HMCS or SMCS consoles are not needed on all systems; but you should have at least one MCS, HMCS or SMCS console capable of operating the sysplex.
It is possible to control a sysplex through SMCS consoles alone. In a sysplex with only SMCS consoles, the hardware management console takes on a more important role; it is the only console to receive synchronous messages, for example.
If you have only SMCS consoles, the hardware management console must be used in place of a NIP console. Consider creating an AUTOACT console group for the system console to provide unbroken communication from NIP to the activation of your SMCS consoles.
Because SMCS consoles connect through a network, security plays a significant role. For example, you need to require operators to log on, and you must take steps to protect the network connections.