query about Join sort

[wuruima]

Hi,

As I know, when we use join stage to join 2 input links, even though we don't set the 'perform sort' in the input link, DS will help to sort. (Is this correct?)

my question is, can we decide to use which function to sort? e.g. use the memory or hard disk to sort.
The default option of Join stage is ?

[Thomas.B]

To see if DataStage sort your data before processing the join operation, just set the APT_DUMP_SCORE to 1 and run it.
In the log you will see the 'Score', if there is a 'tsort operator' for your join, then DataStage sort your data.

By default, when DataStage sort data he use 20MB per partition as an internal memory buffer. When more space is required, he use the 'scratch' disk defined in the APT_CONFIG_FILE.

I don't think you can choose which sort process to use.

[ray.wurlod]

You can only choose which sort process to use by placing an explicit Sort stage on the input links to the Join stage.

You are correct that DataStage will insert a tsort operator by default if you have not otherwise specified sorting on the input links.