Abstract A tape packet assembler/disassembler (TPAD) (7) for a tape drive (25) accumulates host-transmitted records, which may or may not be blocked by the host. The accumulated host-transmitted records are combined into packets (43) comprising a data portion (29) made up of data blocks (31,32) and of a trailer portion (30) made up of table entries (34 through 42) describing how to disassemble the packet. Host-transmitted commands to write a tape mark are intercepted by the TPAD (7) and replaced by corresponding information (47) in the trailer (30). Packets are accumulated in a buffer (13) in the TPAD, and are written to the tape drive (25) when the buffer becomes full, or upon a command from the host to reposition the tape, such as rewind. The interblock gaps that would ordinarily separate the host-transmitted records now separate packets, resulting in a considerable increase in the efficiency of tape utilization. The TPAD maintains in the trailer various pointers (37) to assist in forward and back spacing by file and records. It also can automatically and adaptively compress and decompress the user's data. To assist in this it also maintains in the trailer information (50) identifying data blocks containing a dictionary reset.
Apparatus (7) for assembly and disassembly of packets (43) of data communicated between a host computing environment (1) and a sequentially accessed mass storage device (25) the apparatus comprising: first interface means (8) for coupling to the host computing environment, for receiving host-transmitted records to be written to the mass storage device, and for sending to the host computing environment data and status information read from the mass storage device; tape packet assembly/disassembly means (TPAD) (11 through 22) coupled to the first interface means for assembling into a buffer (13) packets separated by gaps, each packet comprising data portions (14,16,18) (29) and trailer portions (15,17,19) (36) of information corresponding to host-transmitted records, the data portions containing data (31,32) from the host-transmitted records and the trailer portions containing descriptive information (33,37) about the structure of the data portions, including the location of any tape mark that occurred in the host-transmitted record, and for disassembling back into host-transmitted records and associated status indications packets comprising data portions and trailer portions; and second interface means (23) coupled to the TPAD for coupling to the mass storage device (25) for writing packets in the buffer thereto, and for reading packets therefrom into the buffer.
Claim 2
Dependent Claim
200 words
Apparatus (7) for assembly and disassembly of packets (43) of data communicated between a host computing environment (1) and a sequentially accessed mass storage device (25) the apparatus comprising: first interface means (8) for coupling to the host computing environment, for receiving host-transmitted records to be written to the mass storage device, and for sending to the host computing environment data and status information read from the mass storage device; tape packet assembly/disassembly means (TPAD) (11 through 22) coupled to the first interface means for assembling into a buffer (13) packets separated by gaps, each packet comprising data portions (14,16,18) (29) and trailer portions (15,17,19) (36) of information corresponding to host-transmitted records, the data portions containing data (31,32) from the host-transmitted records and the trailer portions containing descriptive information (33,37) about the structure of the data portions, including the location of any tape mark that occurred in the host-transmitted record, and for disassembling back into host-transmitted records and associated status indications packets comprising data portions and trailer portions; and second interface means (23) coupled to the TPAD for coupling to the mass storage device (25) for writing packets in the buffer thereto, and for reading packets therefrom into the buffer.
Claim 3
Dependent Claim
30 words
Apparatus as claimed in claim 1 wherein the TPAD can divide data portions received via the first interface means (8) between packets and records this division in said trailer portions.
Claim 4
Dependent Claim
36 words
Apparatus as claimed in claim 1 or 2 wherein in normal operation writing of data from the buffer (13) via the second interface means (23) to the mass storage device (25) occurs only in complete packets.
Claim 5
Dependent Claim
64 words
Apparatus as claimed in claim 1,2 or 3 wherein a read command is carried out by reading a complete packet of data containing the relevant record to the buffer (13), together with the next succeeding packets until the buffer (13) is full, and using the information in the trailer portions to disassemble the packets before sending relevant record back to the host computing environment.
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