IBM RS/6000 - Manual (Page 85)

Proto Extension Configuration File
As an example, for the PCI-based RS/6000 platform, the file is called rspc.pcfg
and is located in the directory /usr/lib/boot/protoext.
4.3.1.2 RAM File System
When the bosboot command is running, it determines the type of platform and the
boot device for the boot image. It builds the prototype file based on the information
provided by the base proto and proto extension files(4.3.1.1, “Base Proto and Proto
Extension Files” on page 59). Once the prototype file is built, the boot image
generation proceeds as in AIX Version 3, where the RAM file system is first
created, and put together with the stripped kernel image.
The structure of the RAM file system is defined in the base proto files. The RAM
file system must contain all data, commands, libraries, and ODM objects required
during the boot and before the real file systems are mounted from disk, network or
another device.
4.3.1.3 ODM Predefined Database
In AIX Version 3, the Device Configuration Database consists of customized and
predefined objects for all devices supported by AIX. Predefined objects contribute a
major portion of the device database and contain information about all possible
types of devices that can be defined for the system. However, the complete
Predefined Database is not required, nor is it desirable due to its large size. During
boot or installation, only subsets of device information are needed. The problem is
that these subsets are different, depending on the boot and installation devices and
the different phases of the boot process.
In AIX Version 4, the Device Predefined Database is customized to the
configuration of the given system, thus reducing the overall size of the Device
Configuration Database. The whole Predefined Database on a given system is
small enough to fit into the boot image, providing consistent device information for
boot and install across different devices and eliminating the need for subsets and
stanzas files.
ODM Predefined Database
The ODM Predefined Database ( PdDv and PdAt) on PCI-based RS/6000
systems contains definitions and attributes relevant to this platform only.
4.3.2 Structure of the AIX Boot image on PCI-Based RS/6000 Systems
The AIX boot image on PCI-based RS/6000 systems is a combination of a
PReP-compliant partition image and a standard AIX Version 4 boot image, as
shown in Figure 22 on page 62.
Chapter 4. Boot Support and Firmware 61