Specifying the Central Transport Host 
Use
You have set up a common transport directory for (almost) all the SAP Systems in which you want to centrally manage your transports. Furthermore, you can simplify the maintenance of the transport directory by maintaining the directory at a central point.
The advantage of a central transport host is that you only have to maintain one central entry when moving the transport directory to another host, and not the parameters of each system.
To do this, specify the name of the central transport host, where your central transport directory is located, in the domain name server (DNS) for all Windows NT systems.

If you did not specify the
DIR_TRANS = \\$(SAPGLOBALHOST)\sapmnt\trans
Procedure
The transport control program
tp works with its own profile and cannot access the default SAP profiles. The parameter transdir , which is located in this profile, contains the path of the transport directory. You must set this parameter. For a central transport directory, define the parameter using the macro $(SAPTRANSHOST) .
transdir = \\$(SAPTRANSHOST)\sapmnt\trans\
The parameter contains the path of the transport directory and is maintained in the instance-specific profile (if necessary in the default
Normally you should not set this parameter explicitly, since the default value, which points to
\\$(SAPTRANSHOST)\sapmnt\trans\ , usually is correct.If you do not want to store the path under the share
\sapmnt\trans within the transport directory, you can convert parameter DIR_TRANS using the macro $(SAPTRANSHOST) .
DIR_TRANS = \\$(SAPTRANSHOST)\transport
If you do not set the parameter
DIR_TRANS in any profiles, the default value is activated.

If a system for which a central transport host is configured is not supposed to transport a central transport directory, then
override the default values.