How to create static hash files and what it is???

[ICE]

Dear All,

I have being confused with hash files.I have been used hash files in some my jobs for performance matter.But still I don't see the static hash file.I don't know how to create static hash file.May I know what is the difference between static and dynamic hash files?Is it like in other programming language definition???


Thanks,
ice

[ArndW]

One of the options in the hashed file stage lets you not only create the file but also specify what type to create - dynamic or one of the static types. In the Hashed file stage you also can specify a path to the hashed file location or the option of putting it in the project directory.

The difference from your point of view between the two basic types is that dynamic files will grow and shrink the hashing modulus depending upon the file contents and static hashed files do not and need to be sized when they are created. If the modulo of a static hashed file is much too small for the number and type of keys then both reads and writes become slow.

[ICE]

Thanks,ArndW.Here some more questions come.

So,the other file types except dynamic type 30 are static???
I always use dynamic type 30.So I always use dynamic hash files???
Then when should we use the static hash files.
Before this,I always thought static hash file as whenever I create the hash file to use it again in other stage or other jobs is static hash file.
So,that's not correct now.Right???

One of the options in the hashed file stage lets you not only create the file but also specify what type to create - dynamic or one of the static types. In the Hashed file stage you also can specify a path to the hashed file location or the option of putting it in the project directory.

The difference from your point of view between the two basic types is that dynamic files will grow and shrink the hashing modulus depending upon the file contents and static hashed files do not and need to be sized when they are created. If the modulo of a static hashed file is much too small for the number and type of keys then both reads and writes become slow.

[ray.wurlod]

It's not static in the sense of a static variable in C. It's static in the sense that it does not perform automatic space management. Dynamic hashed files do automatically grow and shrink in response to the total volume of data to be stored.

Dynamic (type 30) hashed files are the default because they require the least thought and maintenance.

Static (types 2 through 18) hashed files have to be accurately sized to be efficient, and have to be monitored to ensure that they remain accurately sized.

[ICE]

Ray,
Thank u so much for your help.

Now,i see very clearly. : :D


Thanks,

It's not static in the sense of a static variable in C. It's static in the sense that it does not perform automatic space management. Dynamic hashed files do automatically grow and shrink in response to the total volume of data to be stored.

Dynamic (type 30) hashed files are the default because they require the least thought and maintenance.

Static (types 2 through 18) hashed files have to be accurately sized to be efficient, and have to be monitored to ensure that they remain accurately sized.

[rkdatastage]

Regarding hash files most of the cases dynamic is best as the management of the hash will be done automatically. For better configuration use the Hash File calculator (Hsh.exe) which will be available with Datastage s/w

with regards
rk