The Create a New Virtual Memory Zone routine creates a new
storage zone, according to specified arguments, which is
available to all participants in the application.
Format
PPL$CREATE_VM_ZONE zone-id [,algorithm] [,algorithm-argument]
[,flags] [,extend-size] [,initial-size]
[,block-size] [,alignment] [,page-limit]
[,smallest-block-size] [,zone-name]
1 – Arguments
zone-id
OpenVMS usage identifier
type longword (unsigned)
access write only
mechanism by reference
Zone identifier. The zone-id argument is the address of a
longword set to the zone identifier of the newly created zone.
algorithm
OpenVMS usage longword_signed
type longword (signed)
access read only
mechanism by reference
Algorithm. The algorithm argument is the address of a signed
longword that represents the code for one of the LIB$VM
algorithms:
1 LIB$K_VM_FIRST_ First fit
FIT
2 LIB$K_VM_QUICK_ Quick fit, lookaside list
FIT
3 LIB$K_VM_FREQ_ Frequent sizes, lookaside list
SIZES
4 LIB$K_VM_FIXED Fixed size blocks
If algorithm is not specified, a default of 1 (first fit) is
used.
algorithm-argument
OpenVMS usage longword_signed
type longword (signed)
access read only
mechanism by reference
Algorithm argument. The algorithm-argument argument is the
address of a signed longword that contains a value specific to
the particular allocation algorithm.
Algorithm Value
QUICK_FIT The number of queues used. The number of queues must
be between 1 and 128.
FREQ_SIZES The number of cache slots used. The number of cache
slots must be between 1 and 16.
FIXED The fixed request size (in bytes) for each get or
free. The request size must be greater than 0.
FIRST_FIT Not used, may be omitted.
The algorithm-argument argument must be specified if you are
using the quick-fit, frequent-sizes, or fixed-size-blocks
algorithms. However, this argument is optional if you are using
the first-fit algorithm.
flags
OpenVMS usage mask_longword
type longword (unsigned)
access read only
mechanism by reference
Flags. The flags argument is the address of an unsigned longword
that contains flag bits that control various options:
Bit Value Description
Bit LIB$M_VM_BOUNDARY_ Boundary tags for faster freeing
0 TAGS
Adds a minimum of eight bytes to each
block
Bit LIB$M_VM_GET_FILL0 LIB$GET_VM; fill with bytes of 0
1
Bit LIB$M_VM_GET_FILL1 LIB$GET_VM; fill with bytes of FF
2 (hexadecimal)
Bit LIB$M_VM_FREE_FILL0 LIB$FREE_VM; fill with bytes of 0
3
Bit LIB$M_VM_FREE_FILL1 LIB$FREE_VM; fill with bytes of FF
4 (hexadecimal)
Bit LIB$M_VM_EXTEND_ Add extents to existing areas if
5 AREA possible
Bits 6 through 31 are reserved and must be 0.
This is an optional argument. If flags is omitted, the default of
0 (no fill and no boundary tags) is used.
extend-size
OpenVMS usage longword_signed
type longword (signed)
access read only
mechanism by reference
Zone extend size. The extend-size argument is the address of a
signed longword that contains the number of (512-byte) pages to
be added to the zone each time it is extended.
The value of extend-size must be between 1 and 1024.
This is an optional argument. If extend-size is not specified, a
default of 16 pages is used.
NOTE
Extend-size does not limit the number of blocks that can be
allocated from the zone. The actual extension size is the
greater of extend-size and the number of pages needed to
satisfy the LIB$GET_VM call that caused the extend.
initial-size
OpenVMS usage longword_signed
type longword (signed)
access read only
mechanism by reference
Initial size for the zone. The initial-size argument is the
address of a signed longword that contains the number of (512-
byte) pages to be allocated for the zone as the zone is created.
This is an optional argument. If initial-size is not specified
or is specified as 0, no pages are allocated when the zone is
created. The first call to LIB$GET_VM for the zone allocates
extend-size pages.
block-size
OpenVMS usage longword_signed
type longword (signed)
access read only
mechanism by reference
Block size of the zone. The block-size argument is the address
of a signed longword specifying the allocation quantum (in bytes)
for the zone. All blocks allocated are rounded up to a multiple
of block-size.
The value of block-size must be a power of 2 between 8 and 512.
This is an optional argument. If block-size is not specified, a
default of 8 is used.
alignment
OpenVMS usage longword_signed
type longword (signed)
access read only
mechanism by reference
Block alignment. The alignment argument is the address of a
signed longword that specifies the required address alignment
(in bytes) for each block allocated.
The value of alignment must be a power of 2 between 4 and 512.
This is an optional argument. If alignment is not specified, a
default of 8 (quadword alignment) is used.
page-limit
OpenVMS usage longword_signed
type longword (signed)
access read only
mechanism by reference
Maximum page limit. The page-limit argument is the address of a
signed longword that specifies the maximum number of (512-byte)
pages that can be allocated for the zone. The value of page-limit
must be between 0 and 32,767. Note that part of the zone is used
for header information.
This is an optional argument. If page-limit is not specified or
is specified as 0, the only limit is the total process virtual
address space limit imposed by the OpenVMS operating system.
If page-limit is specified, then initial-size must also be
specified.
smallest-block-size
OpenVMS usage longword_signed
type longword (signed)
access read only
mechanism by reference
Smallest block size. The smallest-block-size argument is the
address of a signed longword that specifies the smallest block
size (in bytes) with a queue for the quick fit algorithm.
If smallest-block-size is not specified, the default of block-
size is used. That is, queues are provided for the first n
multiples of block-size.
zone-name
OpenVMS usage char_string
type character string
access read only
mechanism by descriptor
Name to be associated with the zone being created. The optional
zone-name argument is the address of a descriptor pointing to a
character string containing the zone name. If zone-name is not
specified, the zone does not have an associated name.