Storage Foundation for Oracle RAC Communications

The communications package for Storage Foundation for Oracle RAC consist of LLT and GAB.

Low Latency Transport (LLT)

LLT provides fast, kernel-to-kernel communications, and monitors network connections. LLT serves as a high performance replacement for the IP stack and runs directly on top of the Data Link Protocol Interface (DLPI) layer. The use of LLT rather than IP removes latency and overhead associated with the IP stack. LLT has several major functions.

VCSIPC

RAC Inter-Process Communications (VCSIPC) uses the VCSIPC shared library for inter-process communication. VCSIPC leverages all of LLT's features and uses LMX, an LLT multiplexer, to provide fast data transfer between Oracle processes on different cluster nodes.

Traffic Distribution

LLT distributes (load-balances) inter-node communication across all available private network links. All cluster communications are evenly distributed across as many as eight network links for performance and fault resilience. If a link fails, LLT redirects traffic to the remaining links.

Heartbeat

LLT is responsible for sending and receiving heartbeat traffic over network links. This heartbeat is used by the Group Membership Services function of GAB to determine cluster membership.