These environment variables are useful when running in envirnments with lesser amounts of shared memory such as docker.
This sets the maximum for the audit segment to 2MB and the shared cache to 128MB. By default 1/4 of the ram will be used for the shared cache which can be too much for many systems.
They can be decimal octal or hex values of bytes.
Note that these will be raised to the next value of 2 so the precise amount may vary a little, and also there are segment restrictions which may mean for example that on aix 32bit 256mb gets used for any value below this.