Facilitate migration towards DB2
 

To migrate your data and application to DB2, you must carry out the following operations :

• Migration of data
• Inventory of programs
• Rewrite the programs in SQL language
• Tests
• Validation

Some problems may occur :

• The data in the files are not valid (e.g. a numerical column contains blanks)
• Some program sources do not exist any more
• Rewritten programs do not give the same results as programs prior to migration.
• All the programs must be ready at the same date and migration cannot be performed on a gradual basis.

SQL-TRANSPARENCY facilitates migration to DB2 by ensuring VSAM passage to Relational without modifying the existing application program.
 

Characteristics of SQL-TRANSPARENCY

• Gradual migration of VSAM files to relational data tables
• VSAM compatibility with new relational data thanks to an interface which converts VSAM requests into SQL requests.
• SQL-TRANSPARENCY works just as well with CICS as in Batch environment.
• It is possible to write the user programs in any language (COBOL, Assembler, RPG, PLI...) by using or not a L4G (CSP, Visualgen...). These programs are not, in any way, modified when using transparency..
• It is possible, in the same program, to access VSAM files and relational tables through the transparency interface.

Running SQL-Transparency in an CICS environment.

For a CICS program, a verification is made at each file request. If the file is included in the transparency table as a file to be processed, the VSAM request is replaced by a SQL call.
 

Running SQL-TRANSPARENCY in a BATCH

During the OPEN of the VSAM file, SQL-TRANSPARENCY checks that it is included in the Transparency table.
If the file is found, a modification is made so that SQL-TRANSPARENCY shifts VSAM access onto the DB2 table, during the next operation (READ, WRITE,...).
If the file is not found, the OPEN is done by VSAM and SQL-TRANSPARENCY is not called.
 

Files supported by SQL-TRANSPARENCY

Three types of VSAM files (KSDS, ESDS et RRDS) are supported by SQL-TRANSPARENCY.