Environment       (Dataset - Seg)

DESCRIPTION
The "Environment" shows the name (not the value) of a system environment 
variable that specifies the directory location of a dataset segment. 


VALUES
The "Environment" variable name consists of one to fourteen characters. By 
convention, the name of an "Environment" variable is an uppercase character 
string. The "Environment" variable contains a character string that specifies
a system file system directory. Sun MTPScan obtains the name of the "Environment" 
variable from the Sun MTP File Manager.

To view the value of the "Environment" variable, echo the value at the system
prompt where the Sun MTP system was initiated. For example, if the "Environment"
is 'KIXSYS', view the contents of the variable as follows:

$ echo $KIXSYS


INTERPRETATION
The value of an "Environment" variable specifies the system directory that 
contains a segment's file. The name of the actual file appears in the "Filename"
column of the 'Segments' KxScrolledList. Both are defined in the File Manager. 
Concatenate the "Filename" to the end of the value of the "Environment" for the 
full pathname of the file.


CONCLUSIONS
Sun MTP file segmentation automatically stripes a dataset for both increased file
size and access efficiency. On UNIX systems, each segment can have a size of 2 
Gigabytes, the maximum UNIX file size, allows Sun MTP to access a 16G dataset 
with 8 segments (the maximum number of segments currently allowed by Sun MTP). 
On Windows NT systems, the maximum size of each segment depends on the 
maximum file size offered by the file system in place. For the FAT file system
the maximum file size is 4 Gigabytes. For NTFS, 2 Terabytes is the maximum
file size, although this is constrained by hardware limits rather than NT.

Place segments on different devices (hard disks and/or disk controllers) to 
maximize I/O bandwidth.

Because Sun MTP stores the name of the "Environment", not the value, it is very
easy to change the location of a segment without having to reconfigure Sun MTP. 
To move a segment to a more efficient location, just change the value of its 
"Environment" variable before initiating a Sun MTP system.

Prior to starting a Sun MTP system, the administrator should verify that all
segment "Environment" variables are set correctly and identify valid segment
locations. If an "Environment" variable is set incorrectly, unikixmain.log will 
indicate the segment's problem.
