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Oracle Tips by Burleson Consulting
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SGA memory pinning
In HP/UX and Solaris it is possible to “pin” the SGA so that it will
never experience a page-in. This method is also known as memory
fencing or memory pinning, depending on the UNIX vendor.
Essentially, memory pinning marks the Oracle SGA as being
non-swappable, and the memory region always resides at the
most-recently used area of the RAM heap. Only that memory above and
beyond the Oracle SGA is eligible for paging. On a dedicated Oracle
UNIX server, this technique essentially prioritizes the Oracle SGA,
telling UNIX to page-in only the RAM memory associated with
individual connections to Oracle (PGA memory), and not the Oracle
SGA region.
Please note that not all dialects of UNIX support RAM fencing and
you cannot do RAM memory fencing on IBM-AIX, Linux and other
dialects of UNIX.
In Solaris and HP/UX, the pinning is done by setting the following
init.ora parameters.
lock_sga=true - for hp/ux
USE_ISM=true – Sun Solaris “Intimate Shared Memory”
(Note: In Oracle 8.1.5 and beyond, USE_ISM is a hidden parameter and
defaults to true)
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