Difference between revisions of "RMS Data Files"

Revision as of 16:19, 5 July 2011

On OpenVMS, Recital Terminal Developer and the Recital Database Server support access to the following fixed length RMS File types:

• RMS Sequential
• RMS Indexed Sequential
• RMS Relative

Data access is achieved through an RMS Bridge. This requires the creation of a Bridge file and an empty Recital table that has the same structure as the RMS file.

See Also

ALTER TABLE, CREATE, CREATE BRIDGE, CREATE BRIDGE (SQL), CREATE TABLE, DISPLAY STRUCTURE, LIST STRUCTURE, MODIFY STRUCTURE, SELECT, USE

Creating the Recital Table

Create a Recital table with the same structure as the RMS file. The fields/columns in the structure file must exactly match the data type and length of those in the RMS file. The Recital table will have one byte more in total record length due to the Recital record deletion marker.

To create the table, use the SQL CREATE TABLE command or the Recital Terminal Developer for OpenVMS CREATE worksurface. The table should be given a ’.str’ file extension (rather than the default ’.dbf’) to signify that this is a structure file only.

Please see the end of this document for information on accessing VAX COBOL data types.

Creating the Bridge File

In Recital Terminal Developer for OpenVMS, the Bridge File can be created using the CREATE BRIDGE worksurface. For Recital Database and Mirage Server clients, the Bridge File can be created in two ways: by using an ’ini’ file, or by the SQL CREATE BRIDGE command.

Maximums Widths

The following maximum widths apply to the bridge elements:

CREATE BRIDGE (SQL)

The CREATE BRIDGE SQL command defines and creates the bridge in one step:

exec sql
CREATE BRIDGE rmsseqdemo.dbf 
TYPE "RMSSEQ"
EXTERNAL "rmsseq.dat"
METADATA "rmsseqdemo.str"
ALIAS "rmsseqdemo";

or

exec sql
CREATE BRIDGE rmsseqdemo.dbf
AS "type=RMSSEQ;external=rmsseq.dat;metadata=rmsseqdemo.str;alias=rmsseqdemo";

For RMS Indexed Sequential files, the RMS index keys to be used can also be included in the bridge definition. Up to 7 different keys may be specified:

exec sql
CREATE BRIDGE rmsidxdemo.dbf 
TYPE "RMSIDX"
EXTERNAL "rmsidx.dat"
METADATA "rmsidxdemo.str"
ALIAS "rmsidxdemo"
INDEX "acc_prefix+acc_no,acc_prefix+str(ord_total)";

exec sql
CREATE BRIDGE rmsidxdemo.dbf
AS "type=RMSIDX;external=rmsidx.dat;metadata=rmsidxdemo.str;alias=rmsidxdemo;;
indexkey1=acc_prefix+acc_no;indexkey2=acc_prefix+str(ord_total)";

For RMS Sequential and RMS Relative files, up to 7 Recital single indexes can be built and associated with the bridge.

exec sql
CREATE BRIDGE rmsreldemo.dbf 
TYPE "RMSREL"
EXTERNAL "rmsrel.dat"
METADATA "rmsreldemo.str"
ALIAS "rmsreldemo"
INDEX "ind1.ndx,ind2.ndx,ind3.ndx";

exec sql
CREATE BRIDGE rmsreldemo.dbf
AS "type=RMSREL;external=rmsrel.dat;metadata=rmsreldemo.str;alias=rmsreldemo;;
indexkey1=ind1.ndx;indexkey2=ind2.ndx,indexkey3=ind3.ndx";

CREATE BRIDGE FROM <ini>

Firstly, an ’ini’ file should be created on the server in the data directory where the external data file is held. The ini file has the following contents:

[bridge]
bridgetype=<bridgetype>
externalname=<name of the external data file>
databasename=<name of the Recital structure table>
alias=<the name to use to access your file>
indexkey1=<optional RMS index key or Recital index filename>
indexkey2=<optional RMS index key or Recital index filename>
indexkey3=<optional RMS index key or Recital index filename>
indexkey4=<optional RMS index key or Recital index filename>
indexkey5=<optional RMS index key or Recital index filename>
indexkey6=<optional RMS index key or Recital index filename>
indexkey7=<optional RMS index key or Recital index filename>

rmsreldemo.ini

[bridge]
bridgetype=RMSREL
externalname=rmsrel.dat
databasename=rmsreldemo.str
alias= rmsreldemo
indexkey1=ind1.ndx
indexkey2=ind2.ndx

rmsidxdemo.ini

[bridge]
bridgetype=RMSIDX
externalname=rmsidx.dat
databasename=rmsdemo.str
alias=rmsidxdemo
indexkey1=acc_prefix+acc_no
indexkey2=acc_prefix

NOTE: Recital Terminal Developer users can use the MODIFY BRIDGE to add in details of newly built Recital indexes. In client/server environments the SQL CREATE BRIDGE or 4GL CREATE BRIDGE FROM <ini> command needs to be reissued.

Then the CREATE BRIDGE command should be issued:

create bridge rmsidxdemo.dbf from rmsidxdemo

Using the Bridge

The Bridge can now be used. To access the RMS file, use the ’alias’ specified in the Bridge definition.

Select * from rmsseqdemo

Accessing VAX COBOL Data Types

The following table provides details of the COBOL data types that can be directly accessed by RECITAL using the RECITAL RMS Bridge.

NOTE: The storage occupied packed decimal data types is calculated as follows:

if (n+s) is odd then storage = ((n+s)+1)/2
else storage = ((n+s)+2)/2

When defining the "width" for binary data types, this value denotes the output display width. The storage occupied by the data type is as specified above.

When defining he number of decimal places for binary data types, this value represents the "scale" of the value. When the field is referenced, RECITAL scales it down by successive divisions of 10, as specified by "scale", and evaluates all arithmetic in double precision floating point. When fields of this type are updated, then the result to be stored in the field is again re-scaled.