Planning z/OS® data set encryption

Considerations when planning for data set encryption

  • Encrypted data sets must be extended format. Refer to Extended-Format VSAM Data Sets and Processing Extended-Format Sequential Data Sets for information on allocating extended format data sets, including guidelines and restrictions.
  • Sequential extended format data sets can be version 1 or 2. When allocating an encrypted sequential extended format data set, the system creates the data set as an extended format version 2 data set, regardless of the user's specification for version number on DSNTYPE or the PS_EXT_VERSION keyword in the IGDSMSxx member in PARMLIB.
  • Encrypted data do not compress. Therefore, encrypted extended format data sets might not benefit from storage savings when relying on disk and tape device compression, as well as other areas in the infrastructure that attempt to compress data. Where possible, consider using compressed format data sets. When data set level compression is requested along with encryption, access methods handle compression before encryption for encrypted compressed format data sets. Refer to Compressed Data and Allocating Compressed-Format Data Sets for information on allocating compressed format data sets, including guidelines and restrictions.
  • When processing encrypted extended format data sets, the access methods may use additional internal system buffers during read and write processing. For optimal performance, consider increasing memory to your partition as your use of encrypted data sets increases.
Restrictions for encrypted data sets
  • System data sets (such as Catalogs, SMS control data sets, SHCDS, HSM data sets) must not be encrypted, unless otherwise specified in product documentation.
  • Data sets used during IPL must not be encrypted.
  • Encrypted data sets only supported on 3390 device types.
  • Sequential (non-compressed) data sets with a BLKSIZE of less than 16 bytes cannot be extended format.

For potential restrictions associated with other products, consult the corresponding product documentation.