Introduction to NonStop SQL/MP

Other Architectural Features
NonStop SQL Architecture
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Figure 3-8. Single-Table Query Evaluation Performed by the Data Access Manager
016
LOC QTY PARTNAME
G11 20 16COPPER
•••••••••
90G70 18COPPER
LOC PARTNUM QTY PARTNAME
INVENT Table
(Partition 2)
G68
G98
G92
6032
2002
6402
••• ••••••••••••
•••
2008
3406
5502
•••
23
136
22STEEL
24STEEL
14STEEL
•••
•••
•••
•••
Data access manager evaluates
the table partition and returns
qualified data.
G11
16COPPER
20
G70 90
18COPPER
In Figure 3-8, the partial result retrieved from Partition 2 is sent across the network,
which enhances the value of performing query evaluation before returning data to the
requesting SQL executor. Moreover, in this example, several data access managers can
operate in parallel against the partitions of the INVENT table.
Set-Oriented Update Operations
For a query that updates or deletes data, the data access manager executes the request
and returns an acknowledgment to the file system. This strategy also reduces message
traffic—especially when a set of rows is modified or deleted. Instead of returning
messages and data to the file system for all the rows to be modified, the data access
manager updates the file and sends a single message when it has completed the
operation.
Mixed Workload Environment
The data access manager prioritizes requests to make sure that a long-running query
does not monopolize access to the disk. This feature provides for a mixed workload
environment, which allows a NonStop SQL/MP database to support different
applications that concurrently issue different types of queries.