DBRM

A DBRM (Database Request Module) is the bridge between your COBOL program and DB2. It carries every SQL statement out of your source program and into the BIND process.

What is a DBRM

• DBRM stands for Database Request Module.
• It holds all the SQL statements extracted from your COBOL program by the DB2 precompiler.
• It is stored as a member of a partitioned data set (PDS) called the DBRM library.
• The DBRM is the input to the BIND process. No DBRM, no bind, no running program on DB2.

How a DBRM is created

• The DB2 precompiler (DSNHPC) scans the source program for EXEC SQL ... END-EXEC blocks.
• It produces two outputs: a modified COBOL source (SQL replaced by CALL statements) and the DBRM member.
• One DBRM is created for every program. If a main program calls n subprograms, (n+1) DBRMs are created.
• A timestamp, called the consistency token, is stamped into both the DBRM and the load module.

Role of DBRM in the bind process

• The BIND step reads the SQL from the DBRM, checks syntax and authorization, and lets the optimizer pick access paths.
• The DBRM can be bound directly into a plan (with MEMBER and LIBRARY), or bound into a package first.
• After a successful bind, the DBRM is no longer needed at run time. The plan or package takes over.
• If the timestamp in the load module and the plan/package do not match at run time, the program fails with SQLCODE -818.

Example: precompile step that creates the DBRM

• The step below runs the DB2 precompiler. SYSIN is your source, SYSCIN is the modified source, and DBRMLIB receives the DBRM member:
  
  //PRECOMP EXEC PGM=DSNHPC,REGION=0M, // PARM='HOST(COBOL),SOURCE' //DBRMLIB DD DSN=USERID.DBRMLIB,DISP=(NEW,CATLG,DELETE), // SPACE=(TRK,(10,10,5)),DCB=(RECFM=FB,LRECL=80,BLKSIZE=800) //SYSIN DD DSN=USERID.SOURCE(PROG1),DISP=SHR //SYSCIN DD DSN=USERID.SRCMOD(PROG1),DISP=(NEW,CATLG), // SPACE=(TRK,(10,10,5)) //SYSTSPRT DD SYSOUT=*