D-Pointers

A D-pointer is a special record in a database master dictionary or in a table dictionary that contains information about a table.

The format of a D-pointer is shown below. See the File-Defining Items topic in the D3 Reference Manual for more information.

0 (id)	D3 Table Name
1	D{code}{F,L,N,P,Q,S,T,U,X,Y}
2	Full path name Server: {host file path / } dict {/ data } / file
3	Modulo (hashed Table)

Any field in the full path name can contain D3 environment variables $(name). Environment variablse are useful in encoding the server name and the root path; making moving a table easy. The following names are reserved:

$(MD)	Replaced by the root directory name of the database.
$(MDS)	Replaced by the network computer name of the MDS Server.
$(ROOT)	Replaced by an empty string, indicating the D3 root.

Other environment variables are searched in the table Dm,Catalogue,Environment and replaced with the first attribute of the record that has a key equal to the variable name. The variable name is case insensitive. An environment name can be specified when creating a new table. For example, creating a table on the server $(accounting), on the host driver $(acc.root), where accounting and acc.root are records in the environment file:

accounting

001 Win_301

acc.root

001 D:\Home\Accounting

would actually create the table on the server, Win_301, and place the data under D:\Home\Accounting. Moving this table to another server or another location only requires changing the environment.

NOTE	The optional internal code identifies the type of file. A D-pointer is created automatically by the file system when creating a table. They should not be edited manually nor deleted by a simple delete command.