The write channel program is a logical ring of eight write CCW sets followed by a TIC CCW back to the physical start of the ring. However, because write channel programs use suspend/resume, there is a CCW set between the logical end of the ring and the logical start of the ring that cannot be used. Therefore, a maximum of seven writes can be active at one time. The field CPNCB_index_word contains indexes of the logical first and last CCW sets in the ring and is used to maintain control over the channel program and write completion processing. All CCWs are command-chained together and the suspend bit is on in CCW following the last active write. PCI is always off with the exception that it is sometimes set halfway through the channel program when the channel program is large. As writes complete, PCI and suspend interrupts occur. The structures representing the written data are processed, and if another set of data is waiting for transmission, it is tacked-in to the end of the channel program and the channel program is resumed if it is suspended.

As with a read SECP, a missed tack can occur and it is the responsibility of the interrupt handler to resume the channel program.

The suspend/resume function is implemented for write devices because, unlike read devices where reads remain outstanding, it is expected that during normal operation there will be times when there is nothing to write.