User Guide

Ampex 1308911-02 4-1
Tape Drive Operational Characteristics IntroductionIntroduction
Section 4
Tape Drive Operational Characteristics
4.1 Introduction
The following paragraphs describe tape drive basic behavior (see Table 4-1 and 4-2) you
should be familiar with when using the libdd2 API functions or dd2 utilities.
Table 4-1. DST/DIS Tape Drive Basic Behavior
Platform Default Actions
HP, DEC, Solaris
(device
special file *.0)
On Open:
• Retains current block size.
• Retains current position.
• Clears outstanding Unit Attention conditions.
• Reserves tape drive for exclusive use by initiator.
While Open:
• Allows reformatting of tapes.
• When a filemark is detected during a read, returns the number of bytes read and
sets the current position to after the filemark; the next read gets data from the next
file.
• If a filemark is encountered during the first read after open and no data was
transferred, returns zero bytes.
• Allows appending to and overwriting of existing data.
• Filemarks written to tape are not buffered.
• If EW is encountered during a write, tries to flush the tape drive buffer to tape.
– If successful, returns -1 with errno set to ENOSPC to signify that all data in
the buffer was flushed to tape and the tape/partition is full.
– If unsuccessful, returns the number of bytes written to tape.
On Close:
• If Write was the last command issued before the close, writes a single filemark.
• Flushes the tape drive buffer to tape.
• Sets the current position to BOP.
• Releases the tape drive for concurrent operation.