data_block_size - Advanced SQL Engine - Teradata Database

The maximum data block size for blocks that contain multiple rows.

data_block_size

You can express the value either as a decimal or integer number or using exponential notation. For example, you can write one thousand as either 1000 or 1E3.

This specification is optional. If you do not specify DATABLOCKSIZE, then data blocks default to the sizes set in the PermDBSize and JournalDBSize fields of the DBS Control record For more information about DBS Control settings, see Teradata Vantage™ - Database Utilities , B035-1102 .

For systems without large cylinders, the minimum data block size you can specify is 9,216 bytes (18 sectors). You can specify a value of 8,960 bytes (17.5 sectors), but Vantage rounds that value up to 9,216 bytes internally, and that is the actual data block size the system uses.

For systems with large cylinders, the minimum data block size you can specify is 21,504 bytes (42 sectors). You can specify a value of 21,248 bytes (41.5 sectors), but Vantage rounds that value up to 21,504 bytes internally, and that is the value the system actually uses.

The default values for data block types are determined by DBS Control settings. For detailed information about setting default data block sizes, see Teradata Vantage™ - Database Utilities , B035-1102 .

• For a permanent data block, the default size is determined by the PermDBSize parameter.
• For transient and permanent journals, the default data block size is determined by the JournalDBSize parameter.

BYTES

For BYTES, the value of the data block size is the result of rounding n to the nearest multiple of the sector size in bytes. This is the default.

Rounding is upward when n is exactly halfway between two consecutive multiples.

KBYTES

KILOBYTES

For KILOBYTES, the value of the data block size is the result of rounding 1024n to the nearest multiple of the sector size in bytes.

MINIMUM

The smallest data block size for this table.

MINIMUM DATABLOCKSIZE sets the maximum data block size for blocks that contain multiple rows to the minimum value of 21,504 bytes (42 sectors) for systems with large cylinders or 9,216 bytes (18 sectors) for systems without large cylinders.

You can abbreviate MINIMUM as MIN.

For details about minimum data block sizes, see “DATABLOCKSIZE” in the “CREATE TABLE” section of Teradata Vantage™ - SQL Data Definition Language Detailed Topics , B035-1184 .

MAXIMUM

The largest data block size for this table.

Systems that do not support block sizes 128KB and larger use a value of 127.5KB.

Systems that allow blocks larger than 127.5KB use a maximum of 1,048,064 bytes (2047 sectors) for large cylinders or 262,144 bytes (512 sectors) for small cylinders.

The value can be expressed either as a decimal number or integer number or using exponential notation. For example, you can write one thousand as either 1000 or 1E3.

You can abbreviate MAXIMUM as MAX.

DEFAULT

The default data block size for this table.

If you specify DEFAULT or do not specify a value, Vantage uses the system-wide default data block size specified by the DBS Control setting PermDBSize. For details, see Teradata Vantage™ - Database Utilities , B035-1102 .