1.2.5 Exadata RDMA Memory

Oracle Exadata System Software release 23.1.0 introduces Exadata RDMA Memory (XRMEM). XRMEM incorporates all of the Exadata capabilities that provide direct access to storage server memory using Remote Direct Memory Access (RDMA), enabling faster response times and lower read latencies.

XRMEM encompasses previous Exadata data and commit accelerators based on persistent memory (PMEM), which is only available in Exadata X8M and X9M storage server models. Starting with Exadata X10M, XRMEM enables the benefits of RDMA without needing specialized persistent memory and is primed to leverage developments in memory and storage hardware.

On Exadata X10M systems, workloads requiring ultra-low response times, such as stock trades and IOT devices, can take advantage of XRMEM cache. When database clients read from XRMEM cache, the client software performs an RDMA read of the cached data, which bypasses the storage server software and networking layers, eliminates expensive CPU interrupts and context switches, and delivers results much faster than Exadata Smart Flash Cache. In this case, XRMEM cache operates only in write-through mode, with database writes saved to persistent storage.

On Exadata X10M, XRMEM cache is available on High Capacity (HC) and Extreme Flash (EF) Exadata X10M storage servers, leveraging the high-performance dynamic random-access memory (DRAM) available on the servers. In this environment, XRMEM cache functions automatically, requiring no separate configuration or ongoing administration.

On existing Exadata X8M and X9M systems with Oracle Exadata System Software release 23.1.0, the persistent memory data accelerator, also known as PMEM cache (or PMEMCACHE), is now called the XRMEM cache (or XRMEMCACHE). Likewise, the persistent memory commit accelerator, also known as PMEM log (or PMEMLOG), is now XRMEM log (or XRMEMLOG). However, the CellCLI commands to manage PMEMCACHE and PMEMLOG resources are still available for backward compatibility.

Oracle Exadata System Software release 23.1.0 does not implement XRMEMLOG on Exadata X10M systems.