Initialize Shared-Memory Structures

After the database server attaches to shared memory, it clears the shared-memory space of uninitialized data. Next the database server lays out the shared-memory header information and initializes data in the shared-memory structures. For example, the database server lays out the space needed for the logical-log buffer, initializes the structures, and links together the three individual buffers that form the logical-log buffer. For more information about these structures, refer to the onstat utility in the IBM Informix: Administrator's Reference.

After the database server remaps the shared-memory space, it registers the new starting addresses and sizes of each structure in the new shared-memory header.

During shared-memory initialization, disk structures and disk layout are not affected. The database server reads essential address information, such as the locations of the logical and physical logs, from disk and uses this information to update pointers in shared memory.