In IDMS, what is meant by currency and how does it affect database navigation in an application program?

Introduction / Context:
This question focuses on the idea of currency in CA IDMS. Unlike relational databases where each query specifies explicit rows, IDMS uses the concept of currency to remember which record or set position an application is currently working with. Understanding currency is essential for writing correct navigation logic using DML verbs like OBTAIN, MODIFY, and ERASE in an IDMS environment.

Given Data / Assumptions:

• We are working with IDMS DML in a COBOL program.
• The program executes multiple OBTAIN, STORE, MODIFY, and ERASE statements.
• IDMS internally tracks current positions for records, sets, and areas.
• The question is about this tracking mechanism rather than about monetary values or backup modes.

Concept / Approach:
In IDMS, currency refers to the current record instance or set position that the run unit is pointing to. There can be different levels of currency, such as run unit, record type, set, and area currency. When you issue an OBTAIN or STORE, IDMS updates one or more of these currencies. Subsequent commands that do not specify a full key rely on these currency values to know which record to act upon. The correct answer must explain this role of currency in navigation and DML interpretation.

Step-by-Step Solution:
Step 1: Recall that IDMS navigation often starts with an OBTAIN that sets current of run unit and current of record type. Step 2: Remember that subsequent OBTAIN NEXT or MODIFY statements use the current currency to locate the next or current record. Step 3: Identify the option that describes currency as a concept tracking current position within records and sets. Step 4: Eliminate options that redefine currency as a monetary unit, backup mode, or external log file. Step 5: Confirm that the chosen option reflects how IDMS programmers reason about currency when debugging navigation.

Verification / Alternative check:
A simple way to verify is to think about error messages or debugging output that mention current of record type or current of set. These phrases clearly refer to internal pointers maintained by IDMS. They have nothing to do with money or external logging. Therefore, the explanation that relates currency to tracking current database positions is the only one that aligns with IDMS design and terminology.

Why Other Options Are Wrong:
Option b: Although the word currency is used for money in general English, IDMS uses it in a technical sense unrelated to financial units.
Option c: A backup freeze mode is not called currency in IDMS documentation and would not describe an internal pointer concept.
Option d: External transaction logs are part of journaling or recovery, not of the currency mechanism that guides navigation in a run unit.

Common Pitfalls:
A frequent pitfall is to underestimate how strongly IDMS navigation depends on currency. If a program loses track of currency, OBTAIN NEXT or MODIFY may act on unexpected records. Another mistake is to confuse different levels of currency, such as record type currency versus set currency, leading to logic errors. For exams and interviews, always emphasize that currency means the current position maintained by IDMS to interpret subsequent DML commands.

Final Answer:
Currency is the concept that tracks the current record or set position for an application run unit, affecting how subsequent DML commands interpret OBTAIN and MODIFY requests.