Caché Installation Guide - InterSystems Documentation

the area set aside for global buffers and routine buffers. It uses the following formula to
determine the segment's minimum size:
space required for routine buffers
+ space required for global buffers
+ 4 MB
_____________________________________
= Shared memory segment size
If you are distributing your data across multiple computers, Caché allocates a second segment;
by default, there is no memory allocated for the second segment. (If you plan to use distributed
data, contact your VAR or InterSystems support for configuration guidelines.) You can alter
NBUF and NHBUF according to other system requirements. Because Caché does all its own
disk buffering, you should keep NBUF and NHBUF small. The following table lists the most
common names of the UNIX parameters that you may need to change, the value InterSystems
recommends for each parameter, and a brief description of each. Verify that your parameter
values are set to at least the minimum value. Certain parameters may not be implemented on
all platforms or may be referred to differently. Refer to platform-specific tuning notes for
more information.
Tunable UNIX Parameters
Configure UNIX Kernel Parameters
Kernel
Parameter
CDLIMIT
MSGMAX
MSGMNI
NOFILES
SEMMNI
SEMMNS
Minimum Recommended Value
Number of bytes in largest virtual
volume
2
Number of Caché instances x 2;
each Caché instance uses two
message queues
35
Product of SEMMNI and SEMMSL
must be greater than the # of user
processes + 4
128 or ...
Number of processes expected to
run. If the process table might
expand, use a larger number to
provide for expansion.
Definition
Maximum size of a file.
Maximum message size, in bytes.
Minimum number of uniquely
identifiable message queues that
may exist simultaneously.
Number of open files per process.
Number of semaphore identifiers
in the kernel; this is the number of
unique semaphore sets that can
be active at any one time.
Total number of semaphores in the
system. User processes include
jobbed processes and all other
semaphores required by other
software.
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