MPE/iX was designed to be a ﬁnely-tuned transaction processing machine.
But, as good as it is, MPE isn’t perfect. With the availability of
bigger, cheaper disks, most people don’t think much about disk fragmentation
or contiguous disk space until it’s too late. The system may
mysteriously fail, or, users start complaining about response time, or you
can’t update the OS. Time to look at disk fragmentation.
There are four types of fragmentation found on HP 3000 MPE/iX systems:
disk fragmentation, system fragmentation and
database internal fragmentation. This article focuses on disk fragmentation,
which occurs when the free space on a disk drive is spread throughout
the disk in many small pieces. This can have performance as well as
OS updates and the MPE Transaction Manager (XM) require quite a bit of contiguous space on LDEV 1. Although you may have plenty of disk space available, it may not be contiguous.
What can you do about fragmentation?
Fragmentation normally isn’t harmful, but as mentioned, it can slow your system and actually cause serious problems if contiguous free space
on LDEV 1 gets dangerously low. First, purge all your old log ﬁles. They
accumulate like dust in the corner. Then, reduce the fragmentation. The
easiest way to do this is with a utility, such as De-Frag/X, designed speciﬁcally to reduce disk and ﬁle fragmentation. In case you don’t have one
of these utilities (and why not?), you can use the CONTIGVOL command
of VOLUTIL, ﬁrst introduced with MPE/iX 5.0.
CONTIGVOL is designed to resolve the problem of disk fragmentation,
and does nothing for ﬁle fragmentation, system fragmentation, or database
fragmentation. You use the command to create contiguous space
on LDEV 1.
However, you may run into a problem:
If you run CONTIGVOL and receive an error message “Warning: Contigvol
- Inverse Extent Tbl Full, Internal resource limit,” it simply means
that you’ve run into a minor inconvenience. CONTIGVOL only handles
40,000 extents at a time. You can run it as often as necessary to get
your contiguous space. The message is simply a warning that an internal
table is full.
The bottom line: MPE is great, but not perfect. You still have to manage
your disks, regardless of their apparent inﬁnite capacity.