###### Summary -

In this topic, we described about the below sections -

• DD BLKSIZE

BLKSIZE parameter used to specify the maximum size of the block. BLKSIZE is an optional parameter.

#### Syntax -

```BLKSIZE= {value}
{valueK}
{valueM}
{valueG}
```

 Value Specifies the maximum length in bytes of block.The value specified with BLKSIZE depending the system.Maximum value that can code in bytes is 2,147,483,648.For dummy data sets, the value is 2,147,483,648. ValueK Specifies the maximum length in kilobytes of block.Maximum value that can code in bytes is 2097152K.For dummy data sets, the value is 2097152K. ValueM Specifies the maximum length in Megabytes of block.Maximum value that can code in bytes is 2048M.For dummy data sets, the value is 2048M. ValueG Specifies the maximum length in Gigabytes of block.Maximum value that can code in bytes is 2G.For dummy data sets, the value is 2G.

## Defaults and Overrides:

If the BLKSIZE not coded, system will determine the optimum block size. If a none zero value specified in BLKSIZE parameter in DCB or DD statement, it will override the block size specified in the label.

#### Example 1:

```//NEWFILE DD DSNAME=MTH.INPUT.FILE,DISP=(NEW,KEEP),UNIT=3590,
//            RECFM=FB,LRECL=900,BLKSIZE=9500
```

In the above example, the block size defined as 9500 bytes.

#### Example 2:

```//NEWFILE DD DSNAME=MTH.INPUT.FILE,DISP=(NEW,KEEP),UNIT=3590,
//            RECFM=FB,LRECL=900,BLKSIZE=100K
```

In the above example, the block size defined as 100K. i.e. 100 * 1024 = 102400 bytes.