Shared-memory initialization 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.
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 recovery or at the request of the database server administrator.
Two key differences distinguish shared-memory initialization from disk-space initialization: