Chapter 16. Growing the Oracle SGA to 2.7/3.42 GB in x86 Red Hat Enterprise Linux 3, 4 and 5 Without VLM

16.1. General

Due to 32 bit virtual address limitations workarounds have been implemented in Linux to increase the maximum size for shared memories. A workaround is to lower the Mapped Base Address for shared libraries and the SGA Attach Address for shared memory segments. This enables Oracle to attain an SGA larger than 1.7 GB. To get a better understanding of address mappings in Linux and what Mapped Base Address is, see Section 15.2, “Linux Memory Layout”.
The following example shows how to increase the size of the SGA without a shared memory file system. A shared memory file system must be used on x86 to increase SGA beyond 3.42 GB, see Section 14.8, “Huge Pages and Shared Memory File System in Red Hat Enterprise Linux 3”.