Starting DBRU 19.27 and 23.8 Small Pages Are Not Allowed for RDBMS SGA In Exadata

If you are planning to apply the latest DBRU 19.27 or DBRU 23.8, please be aware of a significant change impacting SGA memory management. Small pages are no longer permitted for the System Global Area (SGA) on Exadata systems.

Attempting to start an Oracle instance configured to use small pages for the SGA will likely fail, and you might encounter the following error:
ORA-27138: unable to allocate large pages with current parameter setting

Your database instance alert log may also report errors related to the use_large_pages parameter, indicating that FALSE, TRUE, or AUTO are no longer supported settings for databases on Exadata.

Why this change?
DBRU 19.27 introduces this restriction to prevent performance and stability issues. Utilizing small 4k memory pages for the SGA can lead to:
    Page table bloat within the virtual machine.
    RDMA resource memory bloat on both the VM and the hypervisor.
    Potential instability affecting the database node and all instances running on it.

Resolution:
To ensure successful database startup and optimal performance after applying these DBRUs, please verify and adjust your large page configuration at the operating system level. For your SGA configuration, we strongly recommend the following:
    Remove memory_target and memory_max_target
    SET sga_target to your desired SGA size.
    Set use_large_pages=ONLY. This is the Maximum Availability Architecture (MAA) recommended value and ensures your entire SGA resides in huge pages on Linux-based systems.

📚 Further Reading & Reference Materials:
    My Oracle Support Note 401749.1: HugePages / Large Pages on Linux
    My Oracle Support Note 361323.1: Checklist for Valid HugePages Setup
    My Oracle Support Note 1392497.1: How to Calculate Recommended HugePages/LargePages Size for Oracle Database
    Oracle Documentation (Doc ID 3081878.1): Starting DBRU 19.27 and 23.8 Small Pages Are Not Allowed for RDBMS SGA In Exadata.

Please take the necessary steps to review your configurations and implement these recommendations to maintain the stability and performance of your Exadata environment.