Hash file

[Bram]

Hi everyone,

Does any body tell me what is hash file, where do we use them and what is exact purpose of hash file in datastage?

Thanks in advance,
Balaram

[ray.wurlod]

Have you searched the forum? Search also for "hashed file", which is the more technically correct name.

In short, a hashed file is a kind of table in which the location of a record is determined by applying an algorithm to the primary key value, rather than performing a table scan or index scan. Key-based access is extremely fast, so they're ideal for key-based reference lookups.

To make these even faster, hashed files (up to a certain size anyway) can be cached in memory, so that access occurs at memory speed rather than disk speed.