Adding a Segment to the Virtual Portion of Shared Memory

The -a option of the onmode utility allows you to add a segment of specified size to virtual shared memory.

You do not normally need to add segments to virtual shared memory because the database server automatically adds segments as needed.

The option to add a segment with the onmode utility is useful if the number of operating-system segments is limited, and the initial segment size is so low, relative to the amount that is required, that the operating-system limit of shared-memory segments is nearly exceeded.