Carmen,
If I'm reading you correctly, these excerpts from SAM's help on configurable kernel parameters may help:
"Allocating system physical memory resources for file system buffer cache space. Includes the
dynamic buffer allocation parameters dbc_min_pct and dbc_max_pct , and the static buffer
allocation parameters bufpages and nbuf ."
" bufpages interacts with XYX as follows:
* bufpages = 0, nbuf = 0: Enables dynamic buffer cache.
* bufpages not zero, nbuf = zero: Creates bufpages/2 buffer headers and allocates (bufpages x4 Kbytes) of buffer
pool space at system boot time.
* bufpages = 0, nbuf not zero: Allocates nbuf*2 pages of buffer pool space and creates nbuf headers at boot time..
* bufpages not 0, nbuf not zero: Allocates bufpages pages of buffer pool space and creates nbuf buffer headers at
boot time. If the two values conflict such that it is impossible to configure a system using both of them, bufpages takes
precedence.
bufpages controls how much actual memory is allocated to the buffer pool. See nbuf.
If bufpages is zero at system boot time, the system allocates two pages for every buffer header defined by nbuf. If
bufpages and nbuf are both zero, the system enables dynamic buffer cache allocation and allocates a percentage of
available memory not less than dbc_min_pct nor more than dbc_max_pct , depending on system needs at any given
time.
The maximum amount of memory that can be allocated to the buffer pool is also affected by the amount of memory allocated
to the system for other purposes. Thus, modifying parameters that affect system memory may also affect the maximum
amount of memory can be made available to the buffer pool. "
"During file-system I/O operations, data is stored in a buffer cache, the size of which can be fixed or dynamically allocated.
When the parameters bufpages and nbuf are both set to their default value of 0, the size of the buffer cache grows or
shrinks dynamically, depending on competing requests for system memory.
The value of dbc_min_pct specifies the minimum percentage of physical memory that is reserved for use by the dynamic
buffer cache.
It is possible to set both dbc_min_pct and dbc_max_pct to the same value, 12 for example, and create a kernel that
uses exactly that percentage of physical memory for the buffer cache, regardless of the size of physical memory. "
"When the parameters bufpages and nbuf are both set to their default value of 0, the size of the buffer cache grows or
shrinks dynamically, depending on competing requests for system memory.
The value of dbc_max_pct sets the maximum percentage of physical memory that can be allocated to the dynamic buffer
cache.
It is possible to set both dbc_max_pct and dbc_min_pct to the same value, 12 for example, and create a kernel that
uses exactly that percentage of physical memory for the buffer cache, regardless of the size of physical memory. "
"This parameter is for backwards compatibility and should be set to zero because dynamic buffer cache is preferred. See
Configurable File-System Buffer Parameters and Overview of File-System Configurable Parameters for more information.
If set to a non-zero value, nbuf specifies the number of buffer headers to be allocated for the file system buffer-cache. Each
buffer is allocated 4096 bytes of memory unless overridden by a conflicting value for bufpages.
If nbuf is set to a non-zero value that is less than 16 or greater than the maximum supported by the system, or to a value
that is inconsistent with the value of bufpages, the number will be increased or decreased as appropriate, and a message
printed at boot time. "
Pete
Pete
