Initialization of the database server refers to two related activities: shared-memory initialization and disk-space initialization.
Shared-memory initialization or bringing up or starting the server establishes the contents of database server shared memory, as follows: internal tables, buffers, and the shared-memory communication area. Shared memory is initialized every time the database server starts up. You use the oninit utility from the command line to initialize database server shared memory and bring the database server online.
Shared-memory initialization also occurs when you restart the database server.
One key difference distinguishes shared-memory initialization from disk-space initialization:
Disk-space initialization uses the values stored in the configuration file to create the initial chunk of the root dbspace on disk. When you initialize disk space, the database server automatically initializes shared memory as part of the process. Disk space is initialized the first time the database server starts up. It is only initialized thereafter during a cold restore or at the request of the database server administrator.