1.82 DB_FLASH_CACHE_SIZE

DB_FLASH_CACHE_SIZE specifies the size of the Database Smart Flash Cache (flash cache). This parameter may only be specified at instance startup.

Property Description

Parameter type

Big integer

Syntax

DB_FLASH_CACHE_SIZE = integer [K | M | G] [, integer [K | M | G]]...

Default value

0

Modifiable

ALTER SYSTEM

Modifiable in a PDB

No

Range of values

Minimum: 0

Maximum: operating system-dependent

Basic

No

You can specify up to 16 file sizes, for each of the flash memory devices specified with DB_FLASH_CACHE_FILE. For example, if there are three flash raw devices, you can specify the sizes of each device as follows:

db_flash_cache_file = /dev/raw/sda, /dev/raw/sdb, /dev/raw/sdc
db_flash_cache_size = 32G, 32G, 64G

If your flash cache consists of one flash cache device, you can dynamically change this parameter to 0 for that flash cache device (disabling the flash cache) after the database is started. You can then reenable the flash cache by setting this parameter for the device back to the original value when the database was started. Dynamic resizing of DB_FLASH_CACHE_SIZE or reenabling flash cache to a different size is not supported.

If your flash cache includes multiple flash cache devices, you can dynamically change the parameter to 0 for a particular flash cache device (turning it off) after the database is started. You can then reenable that flash cache device by setting this parameter for the device back to the original value it had when the database was started (turning it back on).

For example, to turn off the /dev/raw/sdb flash cache device:

db_flash_cache_file = /dev/raw/sda, /dev/raw/sdb, /dev/raw/sdc
db_flash_cache_size = 32G, 0, 64G

And, to turn the /dev/raw/sdb flash cache device back on again:

db_flash_cache_file = /dev/raw/sda, /dev/raw/sdb, /dev/raw/sdc
db_flash_cache_size = 32G, 32G, 64G

See Also:

"DB_FLASH_CACHE_FILE"