17.05 - Row Redistribution Columns - Teradata Database

Teradata Vantageā„¢ - Resource Usage Macros and Tables

prodname
Advanced SQL Engine
Teradata Database
vrm_release
17.00
17.05
created_date
June 2020
category
Administration
User Guide
featnum
B035-1099-170K
Column Name Mode Description Data Type
RRDHCount count Total count of hashed row redistributions (RRDs) processed by the node-level buffered redistribution services (NLB). The RRDHCasc[All|Most|Some] fields count subsets of those RRDs based on the percentage of AMPs in the RRD cascade tree where the rows do not overflow the cascade buffer but are fully contained within the cascade rather than being sent directly to their targeted destination AMPs via NLB's minicast S2S-Redist messages. This percentage is referred to as the "Cascade Factor" and varies between 0% where the RRD rows overflow the cascade buffer in every AMP, and 100% where the rows are cascaded all the way to the cascade root AMP and do not overflow the cascade buffer even there. FLOAT
RRDHCascAll count Count of hashed RRDs with a Cascade Factor of 100%. In this case all rows are cascaded up to the cascade root AMP without overflowing the cascade buffer anywhere, including in the cascade root itself. FLOAT
RRDHCascSome count

Count of hashed RRDs with a Cascade Factor greater than 0% but less than 100%. In this case the rows are cascaded without a buffer overflow in some AMPs, even as few as one, but less than all AMPs.

This field is not equivalent to the Svpr table's similarly named RRDHCascSome field, as it also includes the cases counted in Svpr's RRDHCascMost field.

There is no Sps field (e.g., "RRDHCascNone") that counts the hashed RRDs with a Cascade Factor of exactly 0%, where the rows overflow the cascade buffer in every AMP. However, this virtual count can be computed from the other fields as follows:

RRDHCascNone = RRDHCount - (RRDHCascAll + RRDHCascSome)

FLOAT