Staging
The current Secure Shell protocol, as implemented in third-party
products and current SSH Tectia versions, is designed for Unix files
which are byte streams. MVS data sets are record-based. They must be
staged before sending or destaged after they have been received. Staging
copies a data set into byte stream format and may also convert the
character set. Destaging transforms a byte stream into a file format and
may also convert the character set. Only HFS files that do not need
character set conversion do not need to be staged.
Coming versions of SSH Tectia for z/OS and other platforms will transfer
MVS data sets directly without the need for staging.
Offline staging stores the byte stream as an HFS file. Online staging
places the byte stream in virtual storage when the file is transferred.
SSH Tectia Server (M) includes a utility program, ssh-sft-stage, for
offline staging and destaging. STAGE is a sample of JCL for
running the staging utility (see Appendix STAGE).
The SSH Tectia Server (M) server program will use online staging automatically
if a dataset cannot be transferred directly. Online staging is more
convenient and, for small files, more efficient.
Offline staging incurs the overhead of writing the byte stream to disk
and reading it. Online staging, for large files, will page out most of
the byte stream and will page it in again. Online staging does not
support files that are larger than 2 GB.
The SSH Tectia Server (M) client programs support native MVS dataset reading and
writing and do not require staging. Offline staging is still needed if a
file is transferred to an MVS server and the size of the file is larger
than 2 GB. To use offline staging, you must run the ssh-sft-stage
utility as a separate step.
