Donald K. Burleson
There are many different versions of UNIX, including Solaris, AIX,
SV4, and the new kid on the block, Linux (while Linux has been
around since the early 90's it is just now coming to the fore in
business uses, hence the new kid label.) This subsection provides
general guidelines and some specific suggestions for those systems I
have experience with.
On the install for the general-use database, the MAXDATAFILES
parameter defaults to a value of 100. On older versions of UNIX
there may be a kernel-based limit of 60 open files per process. This
can be overcome by altering the OPEN_MAX value in the limits.h file.
Under some versions of UNIX this may be different; to make the
determination, look under configurable kernel parameters. Another
UNIX-specific limit is on the total number of file extents.
System Global Area (SGA)
In some cases, the SGA may exceed the available shared memory
segment size; if this occurs, the UNIX administrator must relink or
reconfigure the kernel to allow larger programs. There are
system-specific shared memory parameters that control the maximum
size of the SGA. These should be reviewed under configurable kernel
parameters for your version of UNIX. The installation guide for your
Oracle system will delineate which parameters to look at for your
UNIX system. Under the HP-UX implementation the size of the SGA is
limited to the size of swap space on the available disk drives. On a
Sun, True64, or HP-UX system, the parameters that control how the
SGA grows are SHMMAX, the size of a shared memory area, and SHMSEG,
the number of shared memory areas a process can access. On SuSE7.2
and RedHat Linux you can dynamically set the memory and semaphore
processes or load them into the configuration header files and
relink the kernel. On systems such as NT and AIX, you have no
control over memory and semaphore parameters, as they are
automatically set for you.
This is an
excerpt by Mike Ault’s book “Oracle
Administration & Management”. If you want more current Oracle tips
by Mike Ault, check out his new book “Mike
Ault’s Oracle Internals Monitoring & Tuning Scripts” or
Ault’s Oracle Scripts Download.
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