16.10 - Examples of Managed Routing Behavior - Teradata Unity

Teradata Unity User Guide

Product
Teradata Unity
Release Number
16.10
Published
January 2018
Language
English (United States)
Last Update
2018-03-29
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User mappings and routing rules define how session routing occurs based on its logon properties. This table shows examples of managed routing rules and how different rules determine different session routing strategies.
Routing Rule Read System Read Write System Create Write Error Profile
RoutingA TD1 Preferred     DefaultProfile
RoutingB TD1, TD2 Preferred TD1, TD2, TD3 None DefaultProfile
RoutingC TD1, TD2 Default TD1, TD2, TD3 None DefaultProfile
RoutingD TD3, TD1 Preferred TD3, TD1 Preferred DefaultProfile
RoutingE TD1, TD2, TD3 Default TD1, TD2, TD3 Balanced DefaultProfile
DefaultRouting   Default   None DefaultProfile

RoutingA describes a Read-only rule with Preferred routing to a single system. A session is only created on system TD1. All Read requests are sent to system TD1, and Write requests are rejected. A TD1 system failure will return an error to the client. Any errors classified as RESUBMIT will be returned as errors to the client.

RoutingB describes a Read/Write rule with Read routing to Preferred systems TD1, TD2 using Write systems TD1, TD2, and TD3. Sessions are created on TD1, TD2, and TD3. All Read requests are routed to TD1, and only if needed to TD2. Write requests are sent to TD1, TD2, and TD3 depending on which system the data objects reside.

RoutingC describes a Read/Write rule with Default routing. Routing C is identical to Routing B except that it uses automated routing and distributes Reads to both TD1 and TD2 using the shortest queue algorithm to balance the workload.

RoutingD describes a Read/Write rule with Preferred Read routing to TD3, TD1 using Write systems TD3 and TD1. Sessions are created on TD1 and TD3. All Read requests are routed to TD3 and only if needed to TD1. Write requests are sent to both TD3 and TD1. Write requests that also affect data objects on TD2 are rejected. This rule uses Create Preferred routing which means that CREATE statements are executed preferably on TD3 and use TD1 only if TD3 is unavailable.

RoutingE describes a Read/Write rule with automatic Read routing to TD1, TD2, TD3 using Write systems TD1, TD2, TD3. Sessions are created on TD1, TD2, TD3. Read requests are balanced among the systems that resolve each request. Write requests are sent to all systems that contain the data object requested. This rule uses the CREATE ROUTING - BALANCED routing which means that the CREATE statement is executed on one system for each session created. The system used for the CREATE statement for the session is selected from TD1, TD2, TD3 at the start of the session and will not change unless failover occurs on the preferred system.

DefaultRouting describes a Read/Write rule that includes all systems that are managed by Unity at the time of logon. All systems receive both Read and Write requests. Sessions are created on all systems. Read requests are automatically routed using the shortest queue algorithm to load balance across all systems. Write requests are also sent to all systems. The DefaultRouting routing rule always exists and cannot be deleted.

CREATE statements on sessions that do not use the Create Preferred or Create Balanced routing are sent to all systems on the WRITE system list. If both Read Preferred and Create Preferred options are specified, the system lists must be identical because moving or failing over data requires that the new preferred system be able to apply the rules of both the Read Preferred and Create Preferred routing.