7.7.1.12 ALTER PMEMCACHE

Purpose

The ALTER PMEMCACHE command can alter the set of cell disks used by PMEM cache, flush dirty blocks from PMEM cache, or cancel a previous flush operation on the specified cell disks to re-enable caching.

Note:

The ALTER PMEMCACHE command can only be used on Exadata X8M and X9M storage server models.

Syntax

ALTER PMEMCACHE { ALL | CELLDISK="cdisk1 [,cdisk2] ..." [FORCE]}}
      {FLUSH [NOWAIT] | CANCEL FLUSH}

Usage Notes

  • The ALL option affects all available PMEM cell disks.

  • The CELLDISK option allows you to specify individual cell disks. cdiskn represents a cell disk name.

  • The FLUSH option synchronizes dirty data from the PMEM cache to the cell disks. Dirty data is data that has been modified in the cache but not yet synchronized with the data on disk. Synchronization of dirty data can be a lengthy process, depending on the number of bytes to be synchronized. Use the following command to check the progress of the flush operation: 

    LIST CELLDISK ATTRIBUTES name, flushstatus, flusherror

    Note:

    The FLUSH option stops new data from being cached on the PMEM cache until CELLSRV restarts, or the flush operation is canceled with the ALTER PMEMCACHE CANCEL FLUSH command.

  • The CANCEL FLUSH option terminates an earlier flush operation, and reinstates PMEM caching.

  • The NOWAIT option allows the ALTER command to complete while the flush operation is in progress.

  • The FORCE option can be used to forcefully change the set of cell disks used by the PMEM cache.

  • On Exadata X8M and X9M systems with Oracle Exadata System Software release 23.1.0, you can interchangeably use ALTER XRMEMCACHE instead of ALTER PMEMCACHE.

Example 7-64 Using the ALTER PMEMCACHE Command

The following command specifies that the PMEM cache uses all PMEM cell disks. 

CellCLI> ALTER PMEMCACHE ALL

The following command specifies that the PMEM cache uses only two PMEM cell disks, ignoring any errors or warnings. 

CellCLI> ALTER PMEMCACHE CELLDISK='PM_01_mycell, PM_03_mycell' FORCE

The following command specifies initiates a flush operation for all PMEM cell disks, and returns the prompt before the operation completes. 

CellCLI> ALTER PMEMCACHE ALL FLUSH NOWAIT

Parent topic: ALTER