Ensuring that redefined data items have the same starting lengths is crucial when using the REDEFINES clause in COBOL. It helps in preventing data misalignment and memory allocation issues.

The EXIT statement in COBOL can include a numeric operand that specifies the exit code to return to the operating system. This allows the program to communicate its completion status to the calling environment.

Buffering is a technique used in COBOL to enhance performance by temporarily storing records in memory during processing. It reduces the need for frequent disk access, thereby optimizing I/O operations.

When performing database operations, the COMMIT WORK statement is used in COBOL to commit changes made during the transaction to the database. It ensures the changes are permanently saved.

The OCCURS clause in COBOL is used to specify the number of times a group data item or an elementary data item can occur in a table or an array. It defines the occurrence of a particular data item or group.

The COBOL data type PIC X(10) allows you to store both numeric and alphabetic characters in the same field. It is a flexible alphanumeric field that can accommodate a mix of characters.

The "Random" access mode in COBOL is commonly used when working with indexed files to update existing records. It allows direct access to any record in the file based on the key value.

COBOL handles multi-dimensional arrays by using nested OCCURS clauses. This allows the creation of tables with multiple levels, providing a structured way to represent data in multiple dimensions.

To define an array in COBOL using the OCCURS clause, you specify the number of occurrences and the data type of the array elements. This allows the compiler to allocate memory for the array and enables efficient indexing and manipulation of array elements.

In the "ENVIRONMENT DIVISION" of COBOL, the "INPUT-OUTPUT SECTION" is responsible for defining the external data files and devices used by the program. This section specifies the properties and characteristics of input and output operations.

Buffering is a technique in COBOL where frequently accessed records are stored in memory buffers, reducing the need for frequent disk I/O operations and improving overall file handling performance. It helps in minimizing the time required to read or write records from/to external files.

Choosing variable-length records in COBOL can save storage space by avoiding the need to pad unused portions. It is especially beneficial when dealing with data of varying lengths, reducing wasted storage.