Patent EP0212966A2 successfully refreshed from Google Patents.
EP0212966A2
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EP
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Magnetic tape system and method with prefetch control means
Assignee: Fujitsu Ltd
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Filing: 1986-08-18
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Granted: —
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Expires: 2006-08-18
Abstract
Abstract A magnetic tape system including a drive unit (1) with a magnetic head (14), reels (11, 12) for winding a magnetic tape (16) thereon and a drive portion for driving the reels; a drive control unit (2, 20, 21) for controlling the drive unit; and a prefetch control unit (3) having a first memory for prefetching a plurality of commands from the host controller and a second memory for temporarily storing data from the host controller or data read out from the magnetic tape. The drive unit (1) is operated thorugh the drive control unit according to the commands stored in the first memory and the results of the operation are reported to the host controller (5). The prefetch control unit (3) counts the number of blocks (USEG) of write data of the write commands, and when the counted block number is within a free area (FSEG) of the second memory and is larger than the maximum block length (MAXL) allowing prefetching in the second memory, the counted block number (USEG) is set as the new maximum block length (MAXL) and prefetch control of the write data is executed based on the new maximum block length. When the drive control unit detects that the magnetic tape has arrived in the vicinity of the end thereof, the number (AN) of storable write commands to be prefetched and stored in the first memory are reduced by the prefetch control unit.
Inventors
- 👤 Masayuki Ishiguro
- 👤 Noboru Ohwa
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 07:00
CPC Classifications
G; G06; G06F; G06F13/00; G06F13/10; G06F13/12; G06F3/00; G06F3/06; G06F3/0601; G06F3/0668; G06F3/0671; G06F3/0673; G06F3/0682
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
222 words
A magnetic tape system comprising: drive means (1) including a magnetic head (14), reels (11, 12) for winding a magnetic tape (16) thereon, and a drive portion for driving said reels; drive control means (2, 20, 21) operatively connected to said drive means to control said drive means; and prefetch control means (3), operatively connected to said drive control means and to a host controller (5), for feeding access commands to said magnetic tape and having first memory means for prefetching a plurality of commands from said host controller and second memory means for temporarily storing write data from said host controller or data read out from said magnetic tape, said drive means being operated through said drive control means according to the commands stored in said first memory means and results of the operation being reported to said host controller, wherein, in use, said prefetch control means a write counts the number of bytes of write data associated with/ command, and when the counted byte number is within a free area of the second memory means and is larger than the maximum block length (MAXL) allowing prefetching in the second memory means, the counted byte number is set as a new maximum block length and prefetch control of the write data is executed based on said new ' maximum block length.
Claim 2
Dependent Claim
222 words
A magnetic tape system comprising: drive means (1) including a magnetic head (14), reels (11, 12) for winding a magnetic tape (16) thereon, and a drive portion for driving said reels; drive control means (2, 20, 21) operatively connected to said drive means to control said drive means; and prefetch control means (3), operatively connected to said drive control means and to a host controller (5), for feeding access commands to said magnetic tape and having first memory means for prefetching a plurality of commands from said host controller and second memory means for temporarily storing write data from said host controller or data read out from said magnetic tape, said drive means being operated through said drive control means according to the commands stored in said first memory means and results of the operation being reported to said host controller, wherein, in use, said prefetch control means a write counts the number of bytes of write data associated with/ command, and when the counted byte number is within a free area of the second memory means and is larger than the maximum block length (MAXL) allowing prefetching in the second memory means, the counted byte number is set as a new maximum block length and prefetch control of the write data is executed based on said new ' maximum block length.
Claim 3
Dependent Claim
55 words
A magnetic tape system as set forth in claim 1, wherein when said drive control means detects that a current position of the Magnetic tape is in the vicinity of the end thereof, said prefetch control means reduces a storable permitted number (AN) of write commands/to be prefetched and stored in said first memory means.
Claim 4
Dependent Claim
30 words
A magnetic tape system as set forth in claim 2, wherein the reduction of the storable command number is effected whenever a write command from said host controller is received.
Claim 5
Dependent Claim
28 words
A magnetic tape system as set forth in claim 2, or 3, wherein successive reductions of the storable command number are effected down to a predetermined minimum value.
Claim 6
Independent Claim
222 words
A method of operating a magnetic tape system comprising drive means (1) including a magnetic head (14), reels (11,12) for winding a magnetic tape (16) thereon, and a drive portion for driving said reels, drive control means (2,20,21) operatively connected to said drive means to control said drive means, and prefetch control means (3) operatively connected to said drive control means and to a host controller (5), for feeding access commands to said magnetic tape and having first memory means for prefetching a plurality of commands from said host controller and said second memory means for temporarily storing write data from said host controller or data read out from said magnetic tape, said drive means being operated through said drive control means according to the commands stored in said first memory means and results of the operation being reported to said host controller; the method comprising: counting, using said prefetch control means, the number of bytes of write data associated with a write command, and when the counted byte number is within a free area of the second memory means and is larger than the maximum block length (MAXL) allowing prefetching in the second memory means, setting the counted byte number as a new maximum block length and executing prefetch control of the write data based on said new maximum block length.
Claim 7
Independent Claim
222 words
A method of operating a magnetic tape system comprising drive means (1) including a magnetic head (14), reels (11,12) for winding a magnetic tape (16) thereon, and a drive portion for driving said reels, drive control means (2,20,21) operatively connected to said drive means to control said drive means, and prefetch control means (3) operatively connected to said drive control means and to a host controller (5), for feeding access commands to said magnetic tape and having first memory means for prefetching a plurality of commands from said host controller and said second memory means for temporarily storing write data from said host controller or data read out from said magnetic tape, said drive means being operated through said drive control means according to the commands stored in said first memory means and results of the operation being reported to said host controller; the method comprising: counting, using said prefetch control means, the number of bytes of write data associated with a write command, and when the counted byte number is within a free area of the second memory means and is larger than the maximum block length (MAXL) allowing prefetching in the second memory means, setting the counted byte number as a new maximum block length and executing prefetch control of the write data based on said new maximum block length.
References Cited (Backward Citations)
No citation records indexed.
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