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Message Posted: Tue, 23 Nov 2004 @ 17:23:30 GMT
Does anybody know how I can measure the amount of data transferred across the BYNET for multiple queries (% utilization of BYNET can be seen from PMON, but is it maintained in some log file if I need to see for multiple queries)? Also where can I see BYNET bandwidth?
I was curious to know that during redistributions of spool to different amps (Merge joins where Primary indices are different) there would be some records that would come to same amp after rehashing on the basis of join columns. Do they really go to the BYNET or message passing layer for rehashing or are these records never sent to BYNET and directly spooled locally.
For Example consider a table
Table_1 ( Transaction_No Order_No )Primary index (Transaction_no) Records in Table: Transaction_no Order_No 100 100 (Would come back to the same Amp) 101 101 102 102 102 103 (May go to another Amp)
In case I join a Table_1 table to another table Table_2 with same Primary index and structure on basis of order_no (Table_1.order_no = Table_2.order_no) will the first 3 records be moved to bynet and come back to the same amp or would they be spooled locally directly? This is assuming a merge join is happening. It's obvious that the fourth record may go to another AMP.
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