The Comprehensive Guide to Booting a Mainframe Computer System
Booting a mainframe computer system is a complex process that requires careful attention to detail. This guide provides a step-by-step breakdown of the intricate steps involved in starting a mainframe computer, from the initial power supply to the final boot of the operating system.
Understanding Power Supply for Mainframes
When you need to switch a mainframe computer on, the process is not as straightforward as pressing a button. It involves several intricate steps that depend on the nature of the computer and its power supply. Here’s a detailed guide on how to perform this task.
Powering On the System
To start the mainframe, you need to activate the power supply, ensuring that the PC is connected to a live power grid. For many systems, there are additional power switches to consider. For example, a mainframe with two power switches would have one for the master power, capable of delivering 1MWatt, and another for the Uninterruptible Power Supply (UPS).
The UPS is vital as it manages the power cycle, which involves turning on individual racks of batteries. Once the batteries are energized, the alternating current (AC) can be supplied. After this, the master power switch for the computer can be turned on, which then provides power to the dozens of disk drive racks, each equipped with its own power controller.
Initial Power Distribution
Once the power is distributed to the disk drives, they need to stabilize before the system power can be turned on. The system power also has its own power controller, and once it is stable, the systems can begin their boot process.
During this initial stage, the power is provided to the boot systems, which then proceed to boot the IOS (Input/Output System) for the computer. After a few minutes, the boot process is complete, and the mainframe can load the configuration and kernel into the system, verifying the hardware, RAM, and RAID disks.
Final Boot Process
After the boot systems are stable, the mainframe will mount the SSD (Solid State Disk) associated with the IOS, and then mount the UNIX root system disk, defined as a 5-disk RAID configured by the IOS. This process allows the system to begin its full boot sequence.
During the startup, the batch system is initialized, and any running batch jobs are restarted from their checkpoints. This step can take up to half an hour, depending on the complexity of the batch jobs.
System Normalization and User Login
Once the boot process is complete and the system is normalized, users can begin logging in. However, this system can sometimes be dedicated to a single batch job, causing other users to be locked out until the job is finished.
Post-Boot Considerations
It is also important to note that if a forced crash occurs, repair of file systems can be time-consuming. In severe cases, such as a manager forcing a one-time repair, it could take up to two days to complete the necessary repairs.
Conclusion:
Booting a mainframe computer is a process that involves detailed steps and multiple components. By understanding the power supply configuration and the booting sequence, you can ensure a smooth startup and minimize any potential issues.