Reviewing HugePages Memory Allocation

Review this information if your operating system has HugePages enabled.

On Linux platform installations, Oracle recommends that you use HugePages to obtain the best performance for Oracle Databases. When you upgrade Oracle Grid Infrastructure and Oracle Databases on servers that have HugePages enabled, Oracle recommends that you review your HugePages memory allocation requirements.

GIMR and HugePages Memory

Oracle Domain Services Cluster installations include a Grid Infrastructure Management Repository (GIMR), but GIMR configuration is optional for Oracle Standalone Cluster installations. When HugePages is configured on cluster member nodes, the GIMR system global area (SGA) is installed into HugePages memory. The GIMR SGA occupies up to 1 GB of HugePages memory. Oracle Grid Infrastructure starts up before Oracle Databases installed on the cluster.

If your cluster member node operating system memory allocations to HugePages are insufficient for the size of the SGAs for all of the Oracle Database instances on the cluster, then you may find that one or more of your Oracle Database SGAs are mapped to regular pages, instead of Huge Pages, which reduces expected performance. To avoid this issue, when you plan your upgrade, ensure that the memory you reserve for HugePages is large enough to accommodate your memory requirements.

Allocate memory to HugePages large enough for all databases planned to run SGA on the cluster, and to accommodate the SGA for the Grid Infrastructure Management Repository.