Mac OS X

Mac OS X
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When trying to link multiple Berkeley DB language interfaces (for example, Tcl, C++, Java, Python) into a single process, I get "multiple definitions" errors from dyld.
To fix this problem, set the environment variable MACOSX_DEPLOYMENT_TARGET to 10.3 (or your current version of OS X), and reconfigure and rebuild Berkeley DB from scratch. See the OS X ld(1) and dyld(1) man pages for information about how OS X handles symbol namespaces, as well as undefined and multiply-defined symbols.
When trying to use system-backed shared memory on OS X I see failures about "too many open files".
The default number of shared memory segments on OS X is too low. To fix this problem, create a file named /etc/sysctl.conf, containing the variable assignments:
```
kern.sysv.shmmax=134217728
kern.sysv.shmmin=1
kern.sysv.shmmni=32
kern.sysv.shmseg=32
kern.sysv.shmall=1024
```
and then reboot the system.

Check the version of OS X carefully because some versions require all five parameters to be set.

The SHMMAX variable should be set to a value that is an exact multiple of 4096. Some versions of OS X ignore the value if it is not an exact multiple.

Please check and verify with the OS X documentation on the proper setting of these parameters. In some cases a reboot is necessary and in others it is possible to change them dynamically using sysctl.

The /etc/sysctl.conf file exists in OS X 10.3.9 and later. If you are running a version of OS X previous to 10.3.x, edit the /etc/rc file and change the values in the following commands:
```
sysctl -w kern.sysv.shmmax=134217728
sysctl -w kern.sysv.shmseg=32
```
and then reboot the system.

OS X system updates will overwrite /etc/rc so any changes to the file must be redone after sytem updates.

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