Accessing Migrated Datasets

SSH Tectia Server for IBM z/OS can transfer files to and from cataloged, online DASD (direct access storage device) datasets. The following dataset types are supported:

  • uncataloged DASD datasets

  • migrated DASD datasets

  • offline DASD datasets

  • cataloged tape datasets

  • uncataloged tape datasets

  • offline tape datasets

Tape Security

SSH Tectia relies on the system security product for access control to datasets. Because of this, tape datasets must have identifying tape labels. SSH Tectia will not allow the use of NL (No Label) or BLP (Bypass Label Processing). SSH Tectia does not read labels and does not have any label exits.

Operational Security and SSH Tectia Controls

Using an offline tape dataset requires that a tape drive is available and that the tape cassette is mounted on the drive. The operator must mount the drive or cancel the mount request. Outstanding mount requests can cause shortages, locking and deadlocks in resource handling in the system.

Using datasets on offline DASD volumes requires that the operator varies the volume device online. This requires the operator to decide whether the device can be varied online (it is probably offline for a good reason) and to enter the vary command or cancel the request.

Using a migrated dataset requires the system to recall the dataset to a user-accessible (level 0) volume before it can be read or overwritten. If the dataset is on a migration level 1 (DASD) or migration level 2 (tape) volume, it is first copied to level 0.

The z/OS system operators must monitor mount requests to make sure they do not go unanswered or cause problems. They must also monitor the system for SSH Tectia SFT Server processes and SSH Tectia file transfer clients that are hanging on allocation requests for offline datasets.

In SSH Tectia Server for IBM z/OS, mounting an offline dataset is by default not allowed and recalling a migrated dataset is by default allowed.

The SSH Tectia end user controls mounting and recalling with the extended file attributes automount and autorecall. The user must set automount to yes or immed for SSH Tectia to attempt to mount offline datasets. The user can set autorecall to no to avoid recalling a dataset by mistake.

In addition, the administrator must set up access rights to the RACF facility SSZ.MOUNT for the users who will be mounting offline datasets with SSH Tectia client tools for z/OS. For more information, see SSH Tectia Server for IBM z/OS Administrator Manual.

Using Uncataloged Datasets

Existing datasets that do not have entries in the catalog can be accessed by specifying a volume serial number and unit. For example, to read a tape dataset that has the data set name SRVACC1.SPECS.PDF and is the third dataset on volume 456123:

sftp> site unit=TAPE,volumes=456123,dataset_sequence_number=3
sftp> sget //'SRVACC1.SPECS.PDF' /home/clusr1/tmp/specs.pdf

To create a dataset without cataloging it use the normdisp attribute:

sftp> site unit=tape,normdisp=keep
sftp> sput /home/clusr1/tmp/specs-v2.pdf //'SRVACC1.SPECS.V2.PDF'

The dataclass, storclass, and mgmtclass attributes are also available.

Requesting the System to Mount a Volume

For SSH Tectia to request the system to mount an offline volume, you must use the automount=yes attribute. You must also have READ access to SSZ.MOUNT. For example, to read a dataset on a tape volume, assuming that the dataset has a catalog entry, use the following commands:

sftp> site automount=yes
sftp> sget //'SRVACC1.SPECS.PDF' /home/clusr1/tmp/specs.pdf

When automount=yes, SSH Tectia first attempts to allocate the dataset without allowing the system to mount the dataset if it is offline. If this allocation fails, SSH Tectia retries the allocation with the mount request. The user can make SSH Tectia omit the first attempt by specifying automount=immed.

Low-Level Access

SSH Tectia has a facility for low-level access to dynamic file allocation because of the large number of attributes that can be specified when allocating tape datasets.

SSH Tectia allocates datasets by calling the SVC 99 interface. This interface has a table of text units. Each text unit consists of key, parameter count, and parameters. The parameters have a length field and data. The interface is documented in the Authorized Assembler Services Guide.

SSH Tectia allocates files at the start of a file transfer (except if the file is already allocated and is represented by a DD name). SSH Tectia sets text units based on the extended attributes. The svc99_text_units SITE attribute, allows the user to add and change text units in the table. The value of svc99_text_units is a sequence of text units delimited by underscores ('_'). Each text unit has the format xxxxFvalues, where xxxx is the key in hexadecimal, F is a format character and values is a character string. The values part is empty or consists of one string or of several strings delimited by plus signs ('+'). No value may contain spaces, tabs, newlines or any of the characters '_+,/\'. The values part must not exceed 80 characters in length.

The format character indicates how the value(s) are encoded. The possible values are:

  • S: character string

  • X: hexadecimal

  • F: decimal number with length 4 in the text unit

  • H: decimal number with length 2 in the text unit

  • C: decimal number with length 1 in the text unit

  • -: no text unit

When the format character is '-', SSH Tectia removes the text unit with the given key if it is in the table. For the other characters, SSH Tectia replaces the value in the text unit with the given key or adds a new text unit.

The following attributes show how to encode some of the examples in the Authorized Assembler Services Guide. The attributes are not intended to be practical cases.

To specify an accessibility code of Z for an ANSI tape data set:

sftp> site svc99_text_units=8001XE9

To specify a RACF profile that was defined generically and request unallocation when a DCB is closed:

sftp> site svc99_text_units=800EXD9D7D9D6C6+80_001CX

To enter a Key Encode Specification and a Key Label:

sftp> site svc99_text_units=8026SH_8024SLABELQ1.LABELQ2.LABELQ3