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SPD Engine Data Set Options

IOBLOCKSIZE= Data Set Option

Specifies the size in bytes of a block of observations to be compressed.
Valid in: DATA step and PROC step
Affects data set options: COMPRESS= Data Set Option and PADCOMPRESS= Data Set Option
Default: 32,768 bytes





is the size in bytes of a block of observations to be compressed.


The SPD Engine uses blocks in memory to collect the observations to be compressed before they are written to a data component file. IOBLOCKSIZE= specifies the size of these blocks. (The actual size is computed to accommodate the largest number of observations that fit in the specified size of n bytes. Therefore, the actual size is a multiple of the observation length).

Once a compressed data set is created, you cannot change its block size. To resize the block, you must copy the data set to a new data set, setting IOBLOCKSIZE= to the appropriate block size for the output data set.

The default value and the IOBLOCKSIZE= smallest value is 32,768 bytes. You specify an IOBLOCKSIZE= value that complements the data to be accessed. Access to data that is randomly distributed favors a smaller block size, such as 32,768 bytes, because accessing smaller blocks is faster than accessing larger blocks. In contrast, access to data that is uniformly or sequentially distributed or that requires a full data set scan should have a large block size, such as 131,072 bytes.

If the data set is to be updated frequently, use the PADCOMPRESS= Data Set Option to enable expansion between the compressed blocks on the disk.

If a default Base SAS engine data set is copied to the SPD Engine, you do not have to specify COMPRESS= or IOBLOCKSIZE= unless you want to specify a block size other than the default size because compression is retained.

Note:   To add padded space to compressed data sets without changing the compression block size, see PADCOMPRESS= option.   [cautionend]


/*IOBLOCKSIZE set to 64K */
data sport.maillist(ioblocksize=65536 compress=yes);

/*IOBLOCKSIZE set to 32K */
data sport.maillist(ioblocksize=32768 compress=yes);

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