The NON-REPEATABLE READ conditions occur when the COBOL-DB2 program executes the same query multiple times, but the result of the query is different each time. This generally happens when two COBOL-DB2 programs access the same row of the DB2 table.The first program reads the row, then the second program reads ... Read More

The LOST UPDATE and DIRTY read issues are related to concurrency. The concurrency is defined as the ability of two or more applications to access the same table data.The LOST UPDATE impacts the processing of COBOL-DB2 programs in the following way.Suppose there are 2 application programs — PROG A and ... Read More

Problem: A COBOL-DB2 program takes the data from an input file having 1000 records and inserts the data in a DB2 table. The program failed after 432nd record. How will you implement restart logic?SolutionThe restart logic can be implemented in a COBOL-DB2 program by fixing a commit frequency. If we ... Read More

Problem: Explain the difference between Multi-index access and Index-only access paths used by DB2 Optimizer. Give an example for both.SolutionThe Index-only access and Multi-index access are the types of access path which the DB2 optimizer chooses in order to fetch the query results. The Index-only access paths are used when ... Read More

The UNION in DB2 is used to merge two or more SELECT statements. The SELECT statements can be on a single table or on multiple tables. Each SELECT statement is processed individually and their results are combined to give us the final result rows.The UNION statement will eliminate the duplicate ... Read More

The EXECUTE IMMEDIATE and EXECUTE with PREPARE could not be used for SELECT query. For the SELECT query, we have a fixed list SELECT in which the column to be fetched remains fixed and it cannot be changed.For example, if we want to select the orders placed on 14-08-2020. Then ... Read More

The EXECUTE IMMEDIATE and EXECUTE PREPARE are the forms of dynamic SQL. In case of EXECUTE immediate, we can give the SQL statement in the host variable and pass this host variable in EXECUTE IMMEDIATE.Following example demonstrates these forms.Example01 WS-SQL-DECLARE    05 WS-SQL-LEN   PIC S9(04) COMP.    05 WS-SQL-QUERY ... Read More

A static SQL is hardcoded in COBOL-DB2 program and the SQL query cannot change during the program execution. We can only change the value of the host variables. In the case of DYNAMIC SQL, we can change the columns, tables and predicates in the COBOL-DB2 program in run time.For example, ... Read More

The QBLOCK_TYPE column of the PLAN_TABLE mainly gives the information about the type of query. It can have the value as CORSUB which indicates that the query is Correlated subquery and NCOSUB indicates that the query is Non-correlated subquery.The JOIN_TYPE column indicates the type of join used in the query. ... Read More

The PLAN_TABLE in DB2 contains details of the access paths used by the optimizer from the EXPLAIN statement. This table gives much information about the PLAN having DB2 SQL statements.ACCESSTYPE is one of the columns of PLAN_TABLE which gives details regarding the access type. The values which can be present ... Read More