Initial Communication Methods Overview

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Initial Communication Methods Overview

The MIMINIT COMMUNICATION parameter allows you to specify which communications method you want CA MIM to use upon startup.

This table describes the general requirements and benefits for each of the CA MIM communication methods, which are described in more detail in later sections:

Method	Requirements	Benefits
DASDONLY (See note.)	Shareable DASD volume accessible by all systems participating in the MIMplex.	The MIMplex systems can be any combination of sysplexed and non sysplexed images. Solid State DASD provides high performance equivalent to CTC communication options.
CTCONLY	ESCON or FICON CTC devices connecting at least one system to all others in the MIMplex. Definition of at least one CA MIM system to manage the virtual control file (VCF). Definition of at least one checkpoint file on each system in the MIMplex.	The MIMplex systems can be any combination of sysplexed and non-sysplexed images. High performance. Not subject to contention delays associated with DASD IO. Back up master system capability in case of master system failure.
CTCDASD	DASD volume accessible by all systems participating in the MIMplex. ESCON or FICON devices connecting at least one system to all others in the MIMplex. Definition of at least one CA MIM system to manage the virtual control file (VCF).	The MIMplex systems can be any combination of sysplexed and non sysplexed images. High performance. Backup DASD control file capability in case of CTC failure or if there are no available backup masters. Backup master system capability in a master system failure Not subject to contention delays associated with DASD IO when VCF is in use.
NONE	Single system only	Lets you start a CA MIM task on a single system without involving any cross-system communication media. Generally used in new installations for testing purposes.

Although it is required to specify an initial communications method on the MIMINIT COMMUNICATION parameter, you are not constricted to using that communication method during execution (except for COMMUNICATION=NONE). At any time, you can dynamically change communication methods, after correctly configuring an alternate method.

Note: Using the DASDONLY Method

The DASDONLY method uses DASD control files to communicate cross-system information about CA MIM activities. To select this method, specify MIMINIT COMMUNICATION=DASDONLY in the INIT MIM file.

For the DASDONLY or CTCDASD methods, allocate at least one DASD control file. You can allocate up to 99 backup control files. We recommend allocating at least one backup DASD control file for use encase the primary DASD control file becomes unusable.