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What is scratchdisk?
Posted: Mon Nov 15, 2004 12:17 am
by adityaram
Hi,
Im a newbie to the scratchdisk concept. Can someone pl. tell me how it functions.
Thanks in advance.
AR
Posted: Mon Nov 15, 2004 12:59 am
by ray.wurlod
"Scratch disk" is a term that means disk space used temporarily for whatever function might be required, for example to capture the output of a command or query, temporary storage of heaps for sorting, and so on.
Posted: Mon Nov 15, 2004 10:02 am
by kduke
Sometimes called temp space or swap space. In Universe it is defined by UVTEMP.
Posted: Mon Nov 15, 2004 2:44 pm
by ray.wurlod
Swap space is actually something different. Swap space is disk used for memory pages that are not presently in use.
Temp space pointed to be UVTEMP is only relevant for server jobs. In parallel jobs separate scratch space is allocated for each processing node in the configuration file under which the job runs.
Posted: Mon Nov 15, 2004 3:42 pm
by kduke
Ray
I know swap space is not the same as UVTEMP but it is sometimes called scatch space. It functions in a similar manor as UVTEMP for the OS. UNIX also uses /tmp for scatch or temp space.
Re: What is scratchdisk?
Posted: Mon Nov 15, 2004 9:35 pm
by kaziz
adityaram wrote:Hi,
Im a newbie to the scratchdisk concept. Can someone pl. tell me how it functions.
Thanks in advance.
AR
kaziz wrote:
scratchdisk is a term came from Torrent's Orchestrate now Datastage's Parallel Extender. It is the disk space set aside for operation such as sorting or hashing data while processing.
It is defined in configuration file for PX. Orchdisk is permanent disk space such as for datasets. Whereas scratch is not persistent, it is temporary.
Usually on MPP systems these are not NFS mounted, so each node has its own Scratchdisk space.
See APT_CONFIG_FILE env variable pointing to configuration file. Look for scratchdisk defined in node stanza.
Posted: Mon Nov 15, 2004 9:39 pm
by ray.wurlod
The term "scratch disk" has been around since at least 1968. Well before Torrent was even imagined. We had some on an IBM 360/20 at that time.
Posted: Mon Nov 15, 2004 11:33 pm
by T42
Is that the sound of your fingers creaking, Ray?
Bear in mind -- "scratchdisk" (as seen in your configuration file) is totally separate from "disk" -- Datasets disks, which are used exclusively for... Datasets!