How Do I Zip a SAS Dataset?

You can zip a SAS dataset primarily by leveraging external compression tools, such as gzip, through SAS's operating system command interface. This method allows for efficient compression of .sas7bdat files, which is useful for storage, archiving, or transferring large datasets.

Compressing a SAS Dataset with GZIP

To compress a SAS dataset using the gzip tool, you will execute an operating system command directly from within your SAS session. The gzip command will compress the specified SAS dataset file, typically appending a .gz extension to the filename.

Here's an example of how to compress a SAS dataset named crime.sas7bdat located in a specific directory:

/* Define the directory where your SAS dataset is located */
%let sas_data_path = /opt/sasdata; /* Replace with your actual directory path */

/* Compress the SAS dataset using the gzip command */
x "gzip &sas_data_path/crime.sas7bdat";

After executing this code, a compressed file named crime.sas7bdat.gz will be created in the /opt/sasdata directory (or your specified path), and the original crime.sas7bdat file will typically be removed by gzip by default.

Understanding the GZIP Command in SAS

x statement: In SAS, the X statement (or CALL SYSTEM function) allows you to execute operating system commands. This is crucial for interacting with external tools like gzip.
gzip command: This is the command for the GNU zip utility. It's a standard tool on Unix-like operating systems (Linux, macOS) and can also be installed on Windows. For more details on gzip, refer to its official documentation.
&sas_data_path/crime.sas7bdat: This specifies the full path and filename of the SAS dataset you wish to compress. Ensure the gzip utility is installed and accessible in your system's PATH environment variable for SAS to execute it successfully.

Unzipping a GZIP Compressed SAS File

To revert a gzip compressed SAS file (e.g., one with a .gz extension) back to its original .sas7bdat format, you use the gzip -d command, where -d stands for decompress. This command also works for files compressed with the older compress utility, which typically results in .Z extensions.

Here's how you would uncompress a file like crime.sas7bdat.gz:

/* Define the directory where your compressed SAS dataset is located */
%let sas_data_path = /opt/sasdata; /* Replace with your actual directory path */

/* Uncompress the SAS dataset using the gzip -d command */
x "gzip -d &sas_data_path/crime.sas7bdat.gz";

Upon execution, the crime.sas7bdat.gz file will be decompressed, and the original crime.sas7bdat file will be restored in the specified directory. The .gz file will typically be removed.

Note: If you are uncompressing a file with a .Z extension (e.g., crime.sas7bdat.Z), the command would be x "gzip -d &sas_data_path/crime.sas7bdat.Z";. The gzip -d command is versatile and handles both .gz and .Z compressed files.

Key Considerations for Using External Compression:

gzip Availability: Ensure that the gzip utility is installed and accessible on the operating system where your SAS session is running.
Permissions: Verify that SAS has the necessary read/write permissions for the directory containing the SAS dataset and for executing external commands.
Default Behavior: gzip typically replaces the original file with the compressed version and vice-versa. If you need to keep both the original and compressed files, you'll need to use gzip -c > new_file.gz for compression or copy the original file beforehand.
Platform Specifics: While the X statement is standard, the exact path to gzip or its availability might vary slightly across different operating systems.