Transferring Data via Virtual Tape Links

Transferring tape-blocked data with a virtual tape link (between two mvBase processes) requires compatible read/write commands issued at each logical tape unit (LTU) associated with the virtual tape link (VTL). Such command pairs include:

T-DUMP and T-LOAD.
SAVE and RESTORE.
TLOG-DEQUEUE and TLOG-RESTORE.
The mvBASIC WRITET and READT statements.
The T-READ command can be used with any tape write operation to view the data.
Transaction logging and transaction restore.

With each of the above command or function pairs, the VTL assigns read functions to one device and write functions to the other.

The use of VTLs with transaction logging (on the writing device) and transaction restore (on the reading device) supports the operation of Fast Fault Recovery (FFR). FFR provides for hot backup functions on the mvBase Server with an up-to-date image of the primary Server’s database.

NOTE	The operation of update logging, transaction logging, and transaction restore (the system utilities used to implement an FFR strategy) operate in similar fashion with VTLs as they do with other tape devices. FFR with other devices is described in other documentation.

Perform this procedure to transfer data via a virtual tape link (procedure given here serves as an example):

Execute the T-DUMP command for a file on the write LTU. This command line contains required syntax:

Format

T-DUMP [DICT] filename [item-list] [selection] [HEADING "text"] [modifiers] [(options)]

Parameter(s)

DICT	Specifies the file dictionary. When copying dictionary items, the T-DUMP command does not copy any File Definitions to tape.
filename	The name of the file to be written from this device to the read LTU device.
item-list	The list of individual item-IDs. Enclose each item-ID in single quotes.
selection	Specifies one or more conditions that an item must meet in order to be copied. See other documentation of user account commands (the LIST command specifically) for a complete description of selection expression syntax.
"text"	Added to the standard tape label via the HEADING modifier. See other documentation for additional information about MultiValue connectives, modifiers and options.
modifiers	Include one or more parameters that specify the report format. These parameters affect headers, footers, spacing, totaling column figures, control breaks and more. See other documentation for additional information about MultiValue connectives, modifiers and options.
options	Include one or more single-character codes that specify the report format and direct or modify output. They must be enclosed in parentheses, can be entered in any order, and need not be separated by spaces or any delimiters such as commas. See other documentation for additional information about MultiValue connectives, modifiers and options.

Execute the T-LOAD command for the same file on the read LTU. This command line contains required syntax:

Format

T-LOAD [DICT] pipename [item-list] [selections] [modifiers] [(options)]

Parameter(s)

DICT	Specifies the file dictionary. When copying dictionary items, the T-DUMP command does not copy any File Definitions to tape.
pipename	Specific VTL being used.
item-list	List of individual item-IDs. Enclose each item-ID in single quotes.
selection	Specifies one or more conditions that an item must meet in order to be copied. See other documentation of user account commands (the LIST command specifically) for a complete description of selection expression syntax.
modifiers	Include one or more keywords that specify the report format. These parameters affect headers, footers, spacing, totaling column figures, control breaks, and more. See other documentation for additional information about MultiValue connectives, modifiers and options.
options	Include one or more single-character codes that specify the report format and direct or modify output. They must be enclosed in parentheses, can be entered in any order, and need not be separated by spaces or any delimiters such as commas. See other documentation for additional information about MultiValue connectives, modifiers and options.

Operation proceeds with dumping and loading of the selected file item(s) until the T-DUMP command has completed the process and written an EOF (end of file) mark.