7.7.4.8 CREATE PMEMCACHE
Purpose
The CREATE PMEMCACHE
command creates a persistent memory (PMEM)
cache for I/O requests.
Note:
The CREATE PMEMCACHE
command can only be used on
Exadata X8M and X9M storage server models.
Syntax
CREATE PMEMCACHE { ALL [ size = cache_size ] |
CELLDISK='cdisk1[,cdisk2]...' [ , size=cache_size ] }
Usage Notes
-
The
ALL
argument creates the PMEM cache on all PMEM cell disks. If theALL
argument is not specified, then specific PMEM cell disks must be specified by using theCELLDISK
argument. The PMEM cache is spread as evenly as possible across the PMEM cell disks. -
PMEM cache space is allocated in 16 MB chunks, referred to as allocation units, with a minimum of 1 allocation unit. Consequently, when the
size
argument is specified, the actual space allocated to the PMEM cache is at least 16 MB or the largest multiple of 16 MB that is less than or equal to the specified size. For example, ifsize=500M
is specified, then 496 MB is allocated using 31 allocation units. -
Before specifying the
size
attribute, use the following command to check the available free space on the PMEM cell disks:LIST CELLDISK ATTRIBUTES freespace WHERE disktype=PMEM
-
If the
size
attribute is not specified, then the PMEM cache consumes all of the available space (allocation units). -
Cell disks used by the PMEM cache cannot be exported.
-
On Exadata X8M and X9M systems with Oracle Exadata System Software release 23.1.0, you can interchangeably use
CREATE XRMEMCACHE
instead ofCREATE PMEMCACHE
.
Examples
Example 7-88 Creating PMEM Cache
The following command demonstrates how to create a 64 GB PMEM cache on specific PMEM cell disks.
CREATE PMEMCACHE celldisk='PM_01_mycell,PM_02_mycell', size = 64G
The following command demonstrates how to create a 64 GB PMEM cache using all PMEM cell disks.
CREATE PMEMCACHE ALL size = 64G
Parent topic: CREATE