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Background documentationMemory Requirements of a Column Value According to Data Type

 

In the column definition (column_definition), the memory requirement of a column value depends on the data type. You can get an approximate idea of the memory requirement using the following table. Please note that these values are intended as guidance values. Though applicable in most cases, they may vary depending on your system configuration.

Note Note

If the database parameter UseColumnCompression=YES is set, then the space that is actually required is often smaller than the maximum memory requirement. This difference depends on the actual size of the saved column value. See also: Database Administration, Support database parameters

However, if the lead column is not the last lead column, then the actual required space corresponds to the maximum space requirement.

If the column is the last lead column then the actual required space is smaller than the maximum space requirement.

End of the note.
Memory Requirements of a Column Value According to Data Type

Data type

Maximum Space Requirement in the Database (Bytes) UseColumnCompression=YES

Maximum Space Requirement in the Database (Bytes) UseColumnCompression=NO

Space Requirement in Communication (Bytes) when an ASCII Client is Used

Space Requirement in Communication (Bytes) when a UNICODE Client is Used

FIXED(p,s)

(p+1) DIV 2 + 3

(p+1) DIV 2 + 2

(p+1) DIV 2 + 2

(p+1) DIV 2 + 2

FLOAT(p)

(p+1) DIV 2 + 3

(p+1) DIV 2 + 2

(p+1) DIV 2 + 2

(p+1) DIV 2 + 2

BOOLEAN

3

2

2

2

DATE

10

9

11

21

TIME

10

9

9

19

TIMESTAMP

22

21

27

53

CLOB/BLOB

9

9

41

41

CHAR(n) ASCII 0<n<=1023

Key column

n+1

n+1

n+1

2*n+1

CHAR(n) ASCII n<=30

Not a key column

n+2

n+1

n+1

2*n+1

CHAR(n) ASCII 30<n<=254

Not a key column

n+2

n+2

n+1

2*n+1

CHAR(n) ASCII 254<n

Not a key column

n+3

n+3

n+1

2*n+1

CHAR(n) BYTE 0<n<=1023

Key column

n+1

n+1

n+1

n+1

CHAR(n) BYTE n<=30

Not a key column

n+2

n+1

n+1

n+1

CHAR(n) BYTE 30<n<=254

Not a key column

n+2

n+2

n+1

n+1

CHAR(n) BYTE 254<n

Not a key column

n+3

n+3

n+1

n+1

CHAR(n) UNICODE 0<n<=511

Key column

2*n+1

2*n+1

2*n+1

2*n+1

CHAR(n) UNICODE n<=15

Not a key column

2*n+2

2*n+1

2*n+1

2*n+1

CHAR(n) UNICODE 15<n<=127

Not a key column

2*n+2

2*n+2

2*n+1

2*n+1

CHAR(n) UNICODE 127<n

Not a key column

2*n+3

2*n+3

2*n+1

2*n+1

VARCHAR(n) ASCII 0<n<=1023

Key column

n+1

n+1

n+1

2*n+1

VARCHAR(n) ASCII n<=30

Not a key column

n+2

n+2

n+1

2*n+1

VARCHAR(n) ASCII 30<n<=254

Not a key column

n+2

n+2

n+1

2*n+1

VARCHAR(n) ASCII 254<n

Not a key column

n+3

n+3

n+1

2*n+1

VARCHAR(n) BYTE 0<n<=1023

Key column

n+1

n+1

n+1

n+1

VARCHAR(n) BYTE n<=30

Not a key column

n+2

n+2

n+1

n+1

VARCHAR(n) BYTE 30<n<=254

Not a key column

n+2

n+2

n+1

n+1

VARCHAR(n) BYTE 254<n

Not a key column

n+3

n+3

n+1

n+1

VARCHAR(n) UNICODE 0<n<=511

Key column

2*n+1

2*n+1

2*n+1

2*n+1

VARCHAR(n) UNICODE n<=15

Not a key column

2*n+2

2*n+2

2*n+1

2*n+1

VARCHAR(n) UNICODE 15<n<=127

Not a key column

2*n+2

2*n+2

2*n+1

2*n+1

VARCHAR(n) UNICODE 127<n

Not a key column

2*n+3

2*n+3

2*n+1

2*n+1