3.5 Maintaining PMEM Devices on Oracle Exadata Storage Servers

Persistent memory (PMEM) devices reside in Exadata X8M-2 and X9M-2 storage server models with High Capacity (HC) or Extreme Flash (EF) storage.

If a PMEM device fails, Oracle Exadata System Software isolates the failed device and automatically recovers the cache using the device.

If the cache is in write-back mode, the recovery operation, also known as resilvering, restores the lost data by reading a mirrored copy. During resilvering, the grid disk status is ACTIVE -- RESILVERING WORKING. If the cache is in write-through mode, then the data in the failed PMEM device is already stored in the data grid disk, and no recovery is required.

• Replacing a PMEM Device Due to Device Failure
  If the PMEM device has a status of Failed, you should replace the PMEM device on the Oracle Exadata Storage Server.
• Replacing a PMEM Device Due to Degraded Performance
  If a PMEM device has degraded performance, you might need to replace the module.
• Enabling and Disabling Write-Back PMEM Cache