Storage Foundation for Oracle RAC OSD Layer Support

Storage Foundation for Oracle RAC OSD layer support includes the VCSMM and VCSIPC components.

Cluster Membership (VCSMM)

Oracle provides an API called skgxn (system kernel generic interface node membership) to obtain information on membership. Storage Foundation for Oracle RAC implements this API as a library linked to Oracle after you install RAC. The skgxn library makes ioctl calls to a kernel module for membership information.

This module is known as VCSMM (VCS membership module). Oracle 9iR2 uses the shared library libskgxn9.so, which is dynamically linked with the Oracle binary at run-time.

Inter-Process Communications (VCSIPC)

To coordinate access to a single database by multiple instances, Oracle uses extensive communications between nodes and instances. Specifically, Oracle uses Inter-Process Communications (VCSIPC) for lock management traffic and Cache Fusion. Storage Foundation for Oracle RAC uses LLT to support VCSIPC in a cluster and leverages its high-performance and fault-resilient capabilities.

Oracle has an API for VCSIPC, System Kernel Generic Interface Inter-Process Communications (skgxp), that isolates Oracle from the underlying transport mechanism. As Oracle conducts communication between processes, it does not need to know how data moves between systems.

Storage Foundation for Oracle RAC provides a shared library that is dynamically loaded by Oracle at run-time to implement the skgxp functionality. This module communicates with the LLT Multiplexer (LMX) via ioctl calls. The LMX module is a kernel module designed to receive communications from the skgxp module and pass them on to the appropriate process on other nodes. The LMX module "multiplexes" communications between multiple-related processes on the cluster nodes. LMX leverages all features of LLT, including load balancing and fault resilience.