Quantum 1200 Series DAT Autochanger Podręcznik Użytkownika Pobierz pdf (Strona 221)

SDLT 600 SCSI Interface Guide Chapter 4: SCSI Commands

81-81200-02 REV A01 January 2005 4-179

Host vendor-unique attributes can be added and deleted. A write to a host vendor-unique attribute

causes the drive to test the size remaining (Attribute ID 4:MAM Space Remaining) and if the write

does not cause an out-of-memory condition, the drive allows it. An application is allowed to write an

attribute marked as read only to the host vendor-unique area, but this attribute can never be deleted.

NOTE: The format of the host vendor-unique attributes contents are up to the host

to determine.

4.15.4 Unique Features of the SDLT Tape Drive

Implementation of Read / Write Attributes

Keep these features and considerations in mind:

• Super DLTtape media does not support the non-existent state for attributes.

• All attributes that exist are reported in the attribute list and attribute values.

• The SDLT tape drive does not support deleting standard host type attributes (WRITE

ATTRIBUTE commands with attribute length of 0). The only attributes that can be deleted are

host vendor-unique attributes.

• Super DLTtape media only supports ASCII text in the TEXT LOCALIZATION IDENTIFIER

attribute.

• Super DLTtape media does not require that attributes be written (using the WRITE ATTRIBUTE

command) in ascending order. The attributes that can be written are independent of one another

and can be written in any order.

• Since EMAM is written to the tape, there is always a short window during which the tape is loaded

but the attributes have not been read from the tape and stored in RAM. If, during this brief span of

time, the drive receives a READ ATTRIBUTE or WRITE ATTRIBUTE command, it responds

with the Sense Key set to NOT READY, and the Additional Sense Code set to LOGICAL UNIT

NOT READY, MAM NOT AVAILABLE. The application should retry the command in this case.

4.15.5 A Comparison of MAM and EMAM

The SDLT tape drive incorporates a new feature called Enhanced Medium Auxiliary Memory

(EMAM). This feature is used to store MAM attributes in a log file on the tape itself. The attributes are

accessed using the READ ATTRIBUTE and WRITE ATTRIBUTE commands. An EMAM device

mimics a MAM device, with the following exceptions:

• If the tape is bulk erased, the EMAM attribute data is lost. The next time the tape is used, it has

default values in the attribute fields.

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Quantum 1200 Series DAT Autochanger Podręcznik Użytkownika Strona 221