Selectable drive startup (sometimes referred to as selectable boot) allows you to control the startup sequence of the drives in your server. Each time you turn on the server, it checks the drives as it looks for the operating system. The order in which the system checks the drives is the drive-startup sequence.
In most cases, there is no need to change the default drive-startup sequence. However, if users are working with multiple hard disk drives, multiple operating systems, different size diskette drives, or they are planning to do remote initial program load (RIPL) from a drive in a network server, they might want to change the sequence.
The default sequence checks the primary diskette drive for a startable diskette. If one is present, the operating system or program is loaded from the diskette. If not, the system checks the primary hard disk for an operating system. If one is present, the operating system is loaded from that hard disk drive (Ed. Although CDROM is a valid choice on later systems, it is very demanding. Basically, not supported). If not, the system displays either the diskette and F1 prompts or the I9990305 error code.
Example: Default Startup Sequence
If you start the system from a diskette, the drive containing the diskette
becomes drive A, regardless of the defined sequence, and the first hard
disk selected in the startup sequence becomes drive C. You can choose
a startup sequence of up to four drives.
Note: When you change the startup sequence, the drive letters also might change. The operating system assigns the drive letters when the system starts. Letters A and B always are assigned to diskette drives. Also, if a CD-ROM drive has a startable (bootable) CD mounted at startup time, the system views the CD-ROM drive as a diskette drive and assigns it drive letter A or B. Subsequent drive letters can be assigned to any type of drive, based on the operating system or the device drivers used.
Warning: If you changed your startup sequence, you must be extremely careful when doing write operations (for example, copying, saving, or formatting). You can accidentally overwrite data or programs if you select the wrong drive.
To change the startup sequence:
To make a change, use the Up Arrow key or the Down
Arrow key to highlight one of the bracketed items. Use F5 and F6
to scroll through the list of available choices. When you are
finished with your changes, press F10 to save them. If the same drive
is selected twice in the sequence, an asterisk appears next to the second
occurrence to indicate a conflict. You must resolve all conflicts
before you can save the changed sequence.
To Change the Startup Sequence