02-23-2017
Quote:
Originally Posted by
anil529
I checked my database config file , seems the buffers were set to min range
Hold on! If your application is a database then it is usually better to give most memory directly to the database (how this is done depends on the database used: in i.e. Oracle this is called "SGA").
The reason is that DB software makes better use of the memory than the OS is because it can load bigger parts of the DB into memory so that they can be accessed even faster than from disk.
DBs commonly use very specialised ways of accessing their files which circumvent the OSes caching completely anyways (so-called "direct I/O", "concurrent I/O", etc.) so that a reduction of system cache memory won't hurt the DB at all. If you tune a system for a DB as application - as a rule of thumb - you give so much memory directly to the DB that the system just doesn't begin to swap, regardless of how small the file cache will be this way.
I hope this helps.
bakunin
This User Gave Thanks to bakunin For This Post:
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LEARN ABOUT HPUX
vxfs_bc_bufhwm
vxfs_bc_bufhwm(5) File Formats Manual vxfs_bc_bufhwm(5)
NAME
vxfs_bc_bufhwm - VxFS buffer cache high water mark(determines the VxFS buffer cache size)
SYNOPSIS
VALUE
Specify an integer value.
Minimum
6144 KB
Maximum
None
Default
0
DESCRIPTION
VxFS maintains a buffer cache in the kernel for frequently accessed file system metadata in addition to the HP-UX kernel buffer cache that
caches the file data. tunable parameter determines the size of the VxFS buffer cache (the maximum amount of memory that can be used to
cache VxFS metadata).
The default value computed based on the amount of system memory ensures good system performance across a wide range of applications.
The value of is specified in kilobytes. To improve performance during application loads that cause frequent file system metadata changes on
the system (for example, a high rate of file creation or deletion, or accessing large directories), change the value of
Notes
Use the command to monitor buffer cache statistics and inode cache usage.
EXAMPLES
Set the maximum of size of buffer cache at 300000:
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or its meaning may change in the future releases
of HP-UX.
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parameter values. After installation,
some tunable parameters may no longer be at the default or recommended values. For information about the effects of installation on tun-
able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was
factory installed on your system, see at
SEE ALSO
kctune(1M), vxfsstat(1M), vx_maxlink(5), vx_ninode(5), vxfs_ifree_timelag(5).
Tunable Kernel Parameters vxfs_bc_bufhwm(5)