Reconfiguration Coordination Manager (RCM) Script Overview
The Reconfiguration Coordination Manager (RCM) is the framework that manages the dynamic removal
of system components. By using RCM, you can register and release system resources
in an orderly manner.
You can use the new RCM script feature to write your own
scripts to shut down your applications, or to cleanly release the devices from
your applications during dynamic reconfiguration. The RCM framework launches a script automatically in response
to a reconfiguration request, if the request impacts the resources that are registered
by the script.
You can also release resources from applications manually before you dynamically remove the
resource. Or, you can use the cfgadm command with the -f option to
force a reconfiguration operation. However, this option might leave your applications in an
unknown state. Also, the manual release of resources from applications commonly causes errors.
The RCM script feature simplifies and better controls the dynamic reconfiguration process. By
creating an RCM script, you can do the following:
Automatically release a device when you dynamically remove a device. This process also closes the device if the device is opened by an application.
Run site-specific tasks when you dynamically remove a device from the system.
What Is an RCM Script?
An executable shell script (Perl, sh, csh, or ksh) or binary program that the RCM daemon runs. Perl is the recommended language.
A script that runs in its own address space by using the user ID of the script file owner.
A script that is run by the RCM daemon when you use the cfgadm command to dynamically reconfigure a system resource.
What Can an RCM Script Do?
You can use an RCM script to release a device from an
application when you dynamically remove a device. If the device is currently open,
the RCM script also closes the device.
For example, an RCM script for a tape backup application can inform the
tape backup application to close the tape drive or shut down the
tape backup application.
How Does the RCM Script Process Work?
You can invoke an RCM script as follows:
$ script-name command [args ...]
An RCM script performs the following basic steps:
Takes the RCM command from command-line arguments.
Executes the command.
Writes the results to stdout as name-value pairs.
Exits with the appropriate exit status.
The RCM daemon runs one instance of a script at a time.
For example, if a script is running, the RCM daemon does not run
the same script until the first script exits.
RCM Script Commands
You must include the following RCM commands in an RCM script:
scriptinfo – Gathers script information
register – Registers interest in resources
resourceinfo – Gathers resource information
You might include some or all of the following RCM commands:
queryremove – Queries whether the resource can be released
preremove – Releases the resource
postremove – Provides post-resource removal notification
undoremove – Undoes the actions done in preremove
For a complete description of these RCM commands, see rcmscript(4).
RCM Script Processing Environment
When you dynamically remove a device, the RCM daemon runs the following:
The script's register command to gather the list of resources (device names) that are identified in the script.
The script's queryremove and preremove commands prior to removing the resource if the script's registered resources are affected by the dynamic remove operation.
The script's postremove command if the remove operation succeeds. However, if the remove operation fails, the RCM daemon runs the script's undoremove command.