Chapter 6: Using Service Name Redirection

Precedence rules

If you inadvertently create a service name redirection file in which an assigned access service name is not uniquely specified, the system uses the following precedence rules to resolve the problem. The first rule defines the highest precedence, the eighth one the lowest.

**Table 6-2: Precedence rules**
Rule	Description
1	All columns are explicitly defined.
2	requested_service and user_id are specified; application_name uses a wildcard character.
3	requested_service and application_name are specified; user_id uses a wildcard character.
4	user_id and application_name are specified; requested_service uses a wildcard character.
5	Only requested_service is specified; user_id and application_name use wildcard character.
6	Only user_id is specified; requested_service and application_name use wildcard character.
7	Only application_name is specified; requested_service and user_id use wildcard character.
8	Nothing is specified; requested_service, user_id, and application_name use wildcard character.

A null-requested service is treated as any other explicitly-specified service.

Example of precedence ruling

To see how the precedence rules work, assume that you set up the service name redirection file shown in the following table.

**Table 6-3: Example of using the precedence rules**
requested_service	user_id	application_name	assigned_service
AS400	Bob	isql	as1
AS400	*	isql	as2
AS400	*	Omni	omniA
AS400	*	PowerBuilder™	powerB
DB2	*	Omni	db2omni
DB2	*	*	db2gen
<tab>	*	*	as3
*	*	*	as4

Based upon the preceding table, the following are true:

If Bob requests service AS400 using an isql command, he is redirected to service “as1.”
If anyone other than Bob requests AS400 using an isql command, that person is directed to service “as2.”
Anyone who requests service AS400 using Omni is directed to service “omniA.”
Anyone who requests service AS400 using PowerBuilder is redirected to service “powerB.”
Anyone who requests service AS400 using any other application is not redirected. Such requests are connected directly to service “AS400.”
Anyone who requests service DB2 UDB using Omni is directed to service “db2omni.”
Anyone who requests service DB2 UDB using any other application is redirected to service “db2gen.”
All Microsoft and earlier Sybase DB-Library clients for which the requested service name is blank are directed to service “as3.”
Finally, all other clients are routed to service “as4.”

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