CICS VSAM Transparency for z/OS, Version 1.2


DB2 primary table

When CICS® VT intercepts a retrieval call in your program, the DDM accesses the DB2® table that the file maps to. This table is referred to as the primary table.

Figure 1 shows the mapping for a file called VSAM01, and the primary table is called CICSVT.TB_VSAM01.
Figure 1. Primary table mapping
 ------------------- CICS VT: List of fields for VSAM01      Row 1 to  4 of 4 
Command ===> ________________________________________________ Scroll ===> CSR  
                                                                               
VSAM file type : KSDS     Creator   : CICSVT                                 + 
Data set length: 00074    Table name: TB_VSAM01                              + 
                                                                               
Actions: S Display, U Update, I Insert, D Delete                               
                                                                               
A Field    Bytes Start Type DB2 column name                  Exit     Pic Par  
- -------- ----- ----- ---- ------------------------------   -------- --- ---  
_ VSAMKEY  00025 00001   C                                 +             
_ KEYPART1 00020 00001   C  DB2_RECORD_KEY                 +                   
_ KEYPART2 00005 00021   C  DB2_RECORD_TYPE                +                   
_ VSAMDATA 00049 00026   C                                 + MYFBE                  
******************************* Bottom of data ********************************

Assume that an application program issues a START BROWSE for VSAM01. The DDM issues an SQL call to retrieve the appropriate row from DB2. If the row doesn't exist, CICS VT returns an appropriate not found condition to your application. The FBE called MYFBE won't be invoked in this case.

This means that the primary table must contain one DB2 row for every record in the VSAM file.

In some cases, the primary table may contain just those columns that correspond to the VSAM key field. This is the case when your VSAM file copybook redefines the entire record, excluding the key field. The table CICSVT.TB_VSAM01 in Figure 12 is an example and just contains the columns DB2_RECORD_KEY and DB2_RECORD_TYPE.



Concept topic


Last updated: February 8, 2013 20:43:57