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Donald K. Burleson

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UNIX-Specific Notes

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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