IDMS Interview Questions And Answers

Find tells you whether the record is actually in the database. If it is not found you save the overhead of an obtain.

Store the record then connect it to each set where it is a manual member.

Erase cancels the membership of a record in specific set occurrences and removes only the named record.
Erase permanent removes the specific record and all mandatory occurrences it owns. It disconnects all optional members.
Erase selective removes the record, all mandatory members and all optional members not connected to other sets. It disconnects those that are connected.
Erase all removes the specified record and all the mandatory and optional records it owns.

Mandatory and optional.

Currency is the location within the database during run-unit execution.
There are four levels of currency:
current of run-unit is the record occurrence of the last successful find or obtain;
current of record type is for the most recent of each record type;
current of record set is the most recent within each set and current of area is within each area.

It will connect to all sets where it is defined as an automatic member. The store requires that currency be established for all these set occurrences.

IDMS uses record locks to prevent another run-unit from updating the same record.

An area sweep accesses records on the basis of the physical location in a database area. It can be total, meaning a record by record search of the area, or it can be of occurrences of records of a specific type.

You are current on the owner.

A bind associates record types with the program work area; for run unit and records it is the first command issued in the program.

They communicate via service MVS request calls.

No. The mode is specified via the SYSCTL DD card in the JCL.

No difference. There is a difference between obtain first and obtain next for an area sweep, but not when current on the owner in a set.

The schema is the physical arrangement of the data as it appears in the DBMS. The subschema is the logical view of the data as it appears to the application program.

Region is used synonymously with area. It is a group of logically contiguous pages.

A page is the smallest unit of storage in an IDMS database

A record occurrence is the instances of a record; it is the smallest addressable unit of data. A type is the description of a record; there needn't be any occurrences.

In local there is no IDMS System running above the DBMS. It's the more efficient mode but lacks the recovery and integrity facilities of the central version (CV) control program. In CV many application programs access the database through a single copy of the DBMS.

A run-unit is a logical unit of work; it is analogous to a CICS task.

An OOK-Rec is a one of a kind record set, used to get to another record set.

A junction record is a member record type that allows for many-to-many relationship between its two owner records.

Calc is based on a symbolic value which is used to determine the target page. Via mode is for members only. Via records are stored near to their owners.
In direct mode the target is specified by the user and is stored as close as possible to that page.

A set is an owner record and, optionally, its member records. There are three types of pointers: next, prior and owner, but only next is required. There are five possible orders for arrangements of sets; they are: first - insert at beginning, last - insert at end of set, next - insert after current of set, prior - insert prior to current of set and sorted - insert according to sort value.

The READY prepares a database area for access by DML functions.

It writes a checkpoint to the Journal File and releases any record locks.