Solaris (2.5+) Tuning Parameters

• Child processes cannot start under heavy workload?
• Database server reports memory errors while there is plenty free?
• Not taking advantage of external storage cache?

CPU, Memory & Kernel  Network  Disk I/O  Disable Daemons

CPU, Memory & Kernel

ulimit

'ulimit' defines file descriptors limits.  It specifies the number of open files permitted. If this value is set too low, a memory allocation error will occur on Solaris and a too many files open will be logged to the to system error log file. Set this value higher than the default system value. For large multi-processor machines, set to unlimited.

Maximum Number of Processes Per User

'maxuprc' defines the max number of processes each Solaris user can 'fork'. If it is set too low, you may not be able to create high number of database agents necessary to handle connections from your application.  So it is recommended to set this to at least 4096 or higher. 

Solaris Kernel Parameters

Enterprise database servers, such as IBM DB2, provide utilities which recommends Solaris kernel settings given the hardware.  For DB2, for example, the utility is called 'db2osconf'.  The following is the output from a particular Solaris machine.  Many of those settings apply to other database systems.  Add/change them in /etc/system file:

Network

In high volume environment, TCP layer on Solaris should be tuned to the similar values listed below:

Tune TCP

Disk I/O

Tune FS Performance

Update the '/etc/vfstab' file and apply the forcedirectio and noatime parameters. For example:

Enabling file system direct I/O, on Solaris, allows the file system buffer cache to be bypassed which eliminates the double buffering of data which can adversely affect file system I/O performance.  For changes to take effect, you may run 'mount -a', if the file system you are modifying is not mounted. If the file system is mounted it will need to be unmounted and then remounted or a system reboot will need to be executed.

If I/O performance is of the utmost importance, then the utilization of raw devices for database files should be considered. The 'noatime' mount option can improve I/O performance in some cases, for example directories with many files, by not updating the access time of the file. When 'noatime' is not specified; every time a file is accessed the files inode information is updated to reflect the last access time which incurs a write to the file system metadata.

Disable Unused Daemons

To reduce the workload on system make sure you are only running the daemons you need, disabling the unnecessary daemons can significantly improve the load on system.  Know what your Solaris server is used for, and disable the following recommended daemons: