Parallel jobs defined

[ArndW]

BIuser,

to clarify some of the important terms that are often confused or used in an unclear manner:

paging - the act of moving a "page" of memory to a special disk location or returning that page from the location to memory.

swapping - the act of moving a process and it's associated memory to disk or returning it into memory from disk.

The UNIX or Windows systems that are used with datastage all have a limited amount of physical memory that is much smaller than the memory space "seen" by the programs running on them. When more memory is used by the program than is physically present the operating systems will start to move logical memory contents to disk in a process called paging/swapping depending upon what type of memory is being moved. There are various algorithms used by different systems to decided which portions of memory can be removed.

DataStage server and PX jobs will attempt to get as much virtual memory allocated as they can (or are configured to allocate) and with large data volumes or certain types of processing this will almost certainly be more memory than the machine has - thus these programs will have their data dumped out to the paging device during execution and for this reason the manuals give some guidelines as to minimum paging space.

If your paging space is too small your programs will abort during runtime, since DataStage will attempt to allocate more memory but the operating system has no more to give (the total of allocatable memory is the sum of the physical memory plus the paging space).

[ray.wurlod]

Maximum page file size should be at least three times physical memory size.