6.3.5 Monitoring XRMEM Log
Note:
Oracle Exadata System Software release 23.1.0 introduces Exadata RDMA Memory (XRMEM). XRMEM represents the collection of Exadata software technologies that provide direct access to storage server memory using Remote Direct Memory Access (RDMA), enabling faster response times and lower read latencies. In this release, the persistent memory commit accelerator, previously known as PMEM log, is now called XRMEM Log.
Redo log writes are critical database operations and need to complete in a timely manner to prevent load spikes or stalls. Exadata Smart Flash Log is designed to prevent redo write latency outliers. XRMEM log helps to further reduce redo log write latency by using Persistent Memory (PMEM) and Remote Direct Memory Access (RDMA). XRMEM Log is available only in selected Exadata X8M and X9M storage server models.
With XRMEM Log, database clients send I/O buffers directly to PMEM on the
storage servers using RDMA, thereby reducing transport latency. The cell server
(cellsrv) then writes the redo to Exadata Smart Flash Log (if enabled) and disk at a later time.
Reduced redo log write latency improves OLTP performance, resulting in higher transaction throughput. In cases where XRMEM log is bypassed, Exadata Smart Flash Log can still be used.