A system input reader is a physical device that reads system and subsystem commands, control statements, and user jobs to be processed by the operating system. There are three ways to start an input reader:

1. Enter the $S reader command when the device is halted, drained, or inactive.
2. Ready the reader with cards before replying to the initialization message.
3. If your installation has selected the Automatic Start Reader feature, ready the reader with cards at any time, unless the $P reader command is in effect. This feature does not apply to secondary JES2 subsystems.

JES2 provides commands for canceling, halting, and stopping local and remote reader activity ($C, $Z, and $P, respectively). You alter reader characteristics using the $T RDRnn command ($T Rnnnn.RDm for remotes). The $T RDRnn command performs the following functions:

• Assigns command authority for the specified reader
• Specifies default routing, member affinities, and job and message classes for jobs read by the specified reader
• Holds all jobs read by a reader
• Starts or stops tracing of the JES2 processor associated with a reader