Db2 Data Types Guide: COBOL Host Variables, CHAR, DECIMAL, DATE, and LOBs



Column type and COBOL host variable must agree.

A bad data type choice can turn a clean SQL statement into a production defect. A customer amount stored as floating point, a date stored as free text, or a nullable column fetched without an indicator variable can create wrong results before the program ever gets an abend.

Db2 data types define what a column can store, how Db2 compares values, which functions can be used, and how a COBOL host variable should be declared. For mainframe work, the best data type is usually the one that matches the business value and keeps the program's host variables predictable.

Common Db2 data type groups

Group	Db2 data types	Typical use
Exact numeric	SMALLINT, INTEGER, BIGINT, DECIMAL, NUMERIC	Counts, identifiers, money, rates, quantities, and packed business values.
Approximate numeric	REAL, DOUBLE, FLOAT	Scientific or approximate values where rounding is expected. Avoid these for money.
Character	CHAR, VARCHAR, CLOB	Codes, names, descriptions, comments, and long text.
Graphic	GRAPHIC, VARGRAPHIC, DBCLOB	Double-byte character data where the application uses graphic strings.
Binary	BINARY, VARBINARY, BLOB	Bit data, encoded payloads, documents, and other non-character values.
Date and time	DATE, TIME, TIMESTAMP	Business dates, processing times, audit columns, and event timestamps.
Special identifiers	ROWID	Direct row identification where the table design and access path require it.

Db2 and COBOL host variable mapping

In embedded SQL, the column type and the COBOL host variable must be compatible. DCLGEN is often used to generate a starting copybook, but a programmer still has to understand the mapping before changing column definitions or hand-coding host variables.

Db2 column	Typical COBOL host variable	Watch point
CHAR(10)	01 WS-CODE PIC X(10).	Fixed length values can include trailing blanks.
VARCHAR(40)	Group item with length and text fields	COBOL needs the length field and data field, not only PIC X(40).
DECIMAL(9,2)	01 WS-AMT PIC S9(7)V99 COMP-3.	Use packed decimal for business amounts where exact cents matter.
INTEGER	01 WS-COUNT PIC S9(9) COMP.	Binary host variables are common for integer values.
DATE	01 WS-DATE PIC X(10).	Db2 commonly returns ISO format such as 2026-07-07 unless formatting is changed.
TIMESTAMP	01 WS-TS PIC X(26).	Confirm precision and format before moving values to files or screens.
Nullable column	Host variable plus indicator variable	A null value needs an indicator variable; blanks and zero are not null.

Exact numeric types

Use exact numeric types when the value must be stored and compared without approximate rounding. DECIMAL is the normal choice for money, tax amounts, account balances, and rates that need fixed scale. SMALLINT, INTEGER, and BIGINT are better for whole-number counts and technical identifiers.

CREATE TABLE MF_CUSTOMER_BAL
 (ACCT_NO      CHAR(12)       NOT NULL,
  CURR_BAL     DECIMAL(13,2)  NOT NULL,
  PAYMENT_CNT  INTEGER        NOT NULL);

For a COBOL amount such as DECIMAL(13,2), a packed decimal host variable is usually easier to reason about than a display field. Keep the implied decimal position clear in both the copybook and the program move logic.

Character and varying character types

CHAR works well for fixed business codes, such as a two-character country code or a one-character status. VARCHAR fits names, descriptions, and text values where the stored length varies from row to row.

CREATE TABLE MF_ORDER
 (ORDER_ID      INTEGER      NOT NULL,
  ORDER_STATUS  CHAR(1)      NOT NULL,
  CUSTOMER_NAME VARCHAR(60)  NOT NULL);

Do not choose VARCHAR only because it looks flexible. If every value is a fixed two-character code, CHAR(2) is simpler for predicates, display checks, and host variable handling.

Date, time, and timestamp types

Use DATE, TIME, and TIMESTAMP for real calendar and clock values. Storing a date in CHAR(8) may look easy in COBOL, but it pushes validation and comparison work into the program.

CREATE TABLE MF_AUDIT_EVENT
 (EVENT_ID     INTEGER     NOT NULL,
  EVENT_DATE   DATE        NOT NULL,
  EVENT_TS     TIMESTAMP   NOT NULL);

With a real date column, Db2 can compare dates as dates. A predicate such as WHERE EVENT_DATE >= DATE('2026-07-01') is clearer than comparing text strings that might not be in a consistent format.

Large object and binary types

CLOB, BLOB, and DBCLOB are for values larger than ordinary character or binary strings. They are useful for long text, documents, images, and payloads, but they need different program handling from a normal CHAR or VARCHAR column.

Before adding a large object column, check how the application will read it, update it, back it up, and move it through test data. A daily batch extract that once wrote fixed records may need new handling when a CLOB or BLOB appears in the table.

ROWID and distinct types

ROWID identifies a row in a way Db2 can use for direct row access. It is not a business key, and it should not replace a proper primary key such as account number, policy number, or claim number. Use it only when the table design calls for that access pattern.

Db2 also supports distinct types, which let a site create a type based on a built-in type. That can help make two values with the same physical representation mean different things, such as an account identifier and a branch identifier. Check local standards before using distinct types, because they affect SQL, casting, and application code.

How to choose a Db2 data type

Question	Good starting choice
Will the value be used in arithmetic?	DECIMAL for exact business amounts, or integer types for whole numbers.
Is the value a fixed code?	CHAR with the real code length.
Is the value human text with variable length?	VARCHAR, or CLOB for long text.
Is the value a calendar date or event time?	DATE, TIME, or TIMESTAMP.
Can the column be unknown?	Allow null only when the business rule needs it, and code indicator variables in COBOL.
Will the column be searched often?	Choose a type that matches predicates and indexes without frequent casts.

Common mistakes

• Using CHAR for dates and then comparing text instead of real dates.
• Using approximate numeric types for money or balances.
• Changing a column type without checking DCLGEN copybooks, bind steps, and test data.
• Fetching nullable columns without indicator variables.
• Using a larger data type because it feels safer, then paying for bigger indexes and wider rows.

Related DB2 topics

Data types connect directly to Db2 Objects, Db2 Relational Database Anatomy, Db2 Table Spaces, Db2 Indexing, and Db2 Data Types for GET DIAGNOSTICS.

FAQ

Which Db2 data type should be used for money?

Use DECIMAL with the precision and scale required by the business rule. Avoid approximate numeric types for money because rounding can create wrong balances.

Should dates be stored as CHAR in Db2?

Use DATE for calendar dates unless a strict interface rule forces text. Db2 can compare, validate, and format real date columns more reliably than free text.

Does a nullable Db2 column need a COBOL indicator variable?

Yes. When a nullable column is selected into a COBOL host variable, the program should use an indicator variable to detect null. A blank or zero value is not the same as null.

Pick the column type first, then make the COBOL host variable match it. That small discipline prevents many quiet data defects.