User's Manual

• A memory record for PRMID 5, which grants 5 memory shares. The memory cap is 15%.
• A memory record for PRMID 6, which grants 20 memory shares. The memory is isolated—the
group cannot loan or borrow available memory.
Shared memory
A shared memory record is a request that PRM try to keep a minimum number of megabytes of
physical memory available for use as shared memory for the specified PRM group. (As pages in
the shared memory segment are paged out, PRM will attempt to maintain the requested amount
of physical memory for the PRM group. To maintain the current PRM group’s physical memory,
memory in other PRM groups may be paged out more aggressively. PRM does not provide any
method for limiting the shared memory available to a PRM group.)
PRM groups without a shared memory record default to PRM_SYS for shared memory allocation.
NOTE: Note that each shared memory record must be preceded by the #! characters. These
lines are not treated as comments.
The shared memory control feature is supported on HP-UX 11i v2 Update 2 and later.
Use the following syntax to specify a shared memory record:
#!SHARED_MEM:{PRMID|GROUP}:MEGABYTES
where
#!SHARED_MEM Indicates the start of a shared memory record.
PRMID | GROUP Is a PRM group ID or group name for a group that already has a private
memory record. This group ID or group name cannot correspond to a parent
group in a PRM group hierarchy.
You can selectively specify shared memory records: Not every PRM group
must have one.
MEGABYTES Is the size of the desired shared memory allocation for the PRM group in
megabytes. This value serves as a request for a minimum allocation.
The size should reflect the needs of the application in the PRM group. Shared
memory management is optimized for one shared memory segment, such
as one Oracle SGA, per PRM group.
NOTE: If the PRM group uses a larger shared memory segment, it must
borrow the difference. It attempts to borrow the difference from its private
memory allocation first, then from other user-defined PRM groups, and then
from the PRM_SYS group. You should avoid this borrowing, if possible, by
determining how much shared memory a workload allocates and then setting
MEGABYTES to 1.1 times that size.
The minimum MEGABYTES value corresponds to the page size. (Page sizes
can be 4KB, 8KB, 16KB, or 64KB. You must have at least 256 pages, so
the minimum MEGABYTES values are 1, 2, 4, or 16 depending on the
system’s page size.) The maximum value is limited by the available megabyte
value reported by prmavail minus the MEGABYTES values for all shared
memory records and the megabyte value corresponding to the sum of the
SHARES amounts for all memory records.
Consider the following example memory records:
# PRM shared memory records
#!SHARED_MEM:2:10
#!SHARED_MEM:tools/compilers:10
Configuring PRM 61