Technical data

Managing Storage Media
9.3 Initializing Volumes
Table 9–8 (Cont.) INITIALIZE Command Qualifiers
Qualifier Description
/HEADERS=
number-of-headers
Specifies the number of file entries, called file headers, that you expect to have
in INDEXF.SYS, the index file. It controls how much space is initially allocated
to INDEXF.SYS for headers. (The system accesses the index file each time it
locates a file on disk.)
Each file on a disk requires at least 1 file header and each header occupies 1
block within INDEXF.SYS. Files that have many access control entries (ACEs)
or that are very fragmented might use more than 1 header. The default value
of 16 leaves room for fewer than 10 files to be created before INDEXF.SYS must
extend. Therefore, estimate the total number of files that will be created on the
disk and specify it here. A good estimate improves performance of disk access.
Setting the number too low can result in a fragmented index file. However,
if you set the number too high, space allocated to headers cannot be made
available later for file storage and can lead to wasted disk space. This value
cannot be changed without reinitializing the volume.
INDEXF.SYS is limited as to how many times it can extend. When the map
area in its header (where the retrieval pointers are stored) becomes full, files
cannot be created and the message SYSTEM-W-HEADERFULL is displayed.
/INDEX=position Determines the location of the index file on a volume, using the keyword
BEGINNING, MIDDLE, END, or BLOCK:n. The index file lists the names and
addresses of all disk files, so it is constantly referenced.
/MAXIMUM_FILES=n Specifies the maximum number of entries in the index file, and therefore limits
the number of files that a volume can contain. Once set, the maximum number
of files for a volume cannot be increased without reinitializing the disk.
/PROTECTION=
(ownership=[:access][,...])
Specifies the protection code to be assigned to a volume. See Section 9.4 for
details.
/WINDOWS=n Sets the default number of mapping pointers to be allocated for file windows.
When a file is opened, the file system uses mapping pointers to access data
in the file. The file system can read one file segment into memory for each
available pointer.
Caution
The default value for the /HEADER qualifier is generally insufficient
for ODS-2 disks. To improve performance and avoid SYSTEM-F-
HEADERFULL errors, Compaq strongly recommends that you set
this value to be approximately the number of files that you anticipate
having on your disk. However, grossly overestimating this value will
result in wasted disk space.
Examples
1.
$ INITIALIZE/HEADERS=100000 DUA3:
This example shows how many entries to allocate in the index files for a large
disk (a small disk might allocate 2000 entries).
2.
$ INITIALIZE/MAXIMUM_FILES=20000 DUA3:
This example shows how to specify the characteristics of a small disk. Note
that each directory and each extension header of a multiheader file counts as
a file against this maximum value.
Managing Storage Media 9–19