Communicator e3000 MPE/iX Release 7.5 (Software Release C.75.00) (30216-90336)

Chapter 5
Technical Articles
Support for Using the Entire Disk Space on LDEV 1
110
Support for Using the Entire Disk Space on LDEV 1
By Ushadevi H N, Commercial Systems Division
Beginning with MPE/iX 7.5 release, the MPE/iX operating system uses the full capacity of the disk configured
as LDEV 1. This article explains the enhancement and briefly describes the user level changes for customers
to use the system appropriately after installing MPE/iX 7.5 release.
Background
Before the 7.5 release, MPE/iX limited the access on LDEV 1 to only the first 4GB of the total disk space with
the rest of the disk unavailable for use.
Primarily, this limitation existed because the initial system loader (ISL> prompt) could access only the first
4GB of the disk. System utilities such as START, DUMP, and DISCUTIL need to reside in the first 4GB of
the disk. As a result, LDEV 1 disk access overall was limited to 4GB of the disk space.
With this enhancement, the operating system can utilize the entire disk space for storing other files. Because
the ISL limitation is not removed, system utilities still need to be stored within the first 4GB of the disk.
Hardware and Software Requirements
This enhancement is enabled by default once the MPE 7.5 version of the operating system (Release C.75.00) is
installed. This feature applies to all HP supported disks and disk arrays, regardless of the disk capacity.
NOTE Even though this feature is to take advantage of all disks greater than 4GB, only disks with a
capacity greater than (or equal to) 5GB will have their extra capacity available for use.
Enhancement Details
For disks configured as LDEV 1, this enhancement distinguishes between files residing within 4GB and those
beyond 4GB. Proper functioning of the MPE/iX operating system requires that some specific system utilities
reside in the first 4GB of the disk. Therefore, user files targeted for LDEV 1 are stored in the first 4GB under
only two circumstances:
• If there is not enough space beyond the first 4GB to accommodate the file.
• When forced by the file equate option described below.
HP highly recommends that user files be kept in the disk space beyond 4GB to preserve space for system files,
now and in the future. A new designator is provided to differentiate and help users keep files within or
beyond 4GB.
;DEV=**$SYSTEM_MASTER
The device designator $SYSTEM_MASTER is now used to refer to the file space within the first 4 GB of LDEV 1.
Using $SYSTEM_MASTER in file commands such as BUILD and FILE, and in file intrinsics (for example,
HPFOPEN) will create and refer to files within the first 4 GB.
EXAMPLE: Creating files within the first 4GB of LDEV 1
Prior to 7.5 all installation tools/applications, such as PATCH/iX, AUTOINST, HPINSTAL,
AUTORESTART/iX, etc., use the following equation to create AXLDEV1 (for the purpose of reserving space):
: BUILD AXLDEV1;DISC=n,1,1;DEV=1