Data set information for recovery of synchronized data on magnetic tape

• US 6,865,043 B2
• Filed: 11/14/2002
• Issued: 03/08/2005
• Est. Priority Date: 01/29/2002
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Ataku, Toshimi, Itagaki, Hiroshi, Jaquette, Glen Alan, Greco, Paul Merrill, Shiratori, Toshiyuki, Nagura, Hironobu
• Primary Examiner(s): Tran, Sinh
• Assistant Examiner(s): DAVIDSON, DAN
• Application Number:
  US10/293,550
• Publication Number:
  US 20030142429A1
• Time in Patent Office: 845 Days
• Field of Search: 360/48, 360/72.1, 360/72.2, 710/6, 710/52, 711/167
• US Class Current: 360/48
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0682 Tape device
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: G11B 20/1201 on tapes
• CPC Class Codes: G11B 20/1403 characterised by the use of two levels
• CPC Class Codes: G11B 2020/1062 Data buffering arrangements, e.g. recording or playback buffers
• CPC Class Codes: G11B 2220/216 Rewritable discs
• CPC Class Codes: G11B 2220/90 Tape-like record carriers
• CPC Class Codes: G11B 2220/95 Serpentine format, wherein a single track or group of tracks traverses the tape plural times from one end to the other
• CPC Class Codes: G11B 27/3027 used signal is digitally coded

Abstract

Special fields for error recovery are provided in data set information tables of data sets written with synchronized transactions. If a transaction only partially fills a data set, that data set is rewritten in a succeeding data set, appending the next transaction. A moving access point in the table identifies the appended transaction, allowing the rewritten transaction to be skipped during read recovery. The table provides recovery trails by providing a thread to tie the data sets together, the status of the data set, and pointers, such as identifying the wrap of the immediately succeeding data set.

Claims

1. A recording system for a magnetic tape drive, said magnetic tape drive having at least one motor for moving a magnetic tape longitudinally;

said magnetic tape drive having at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor;

said magnetic tape drive for receiving data to be written to said magnetic tape, said recording system comprising;

at least one recording channel receiving said data to be written to said magnetic tape, said data in the form of transactions, and said at least one recording channel for operating said at least one read/write head for writing transactions to said magnetic tape; and

a controller operating said at least one motor, and said at least one recording channel, said controller;

detects a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

writes said synchronized transactions to said magnetic tape as written synchronized transactions, in the form of data sets, each data set having a data set information table;

in the event one of said written synchronized transactions partially fills a data set, rewrites said partially filled data set in a succeeding data set, appends a subsequent said synchronized transaction in said succeeding data set as an appended synchronized transaction; and

establishes a moving access point for said succeeding data set in said data set information table of said succeeding data set, said moving access point identifying said appended synchronized transaction, thereby skipping said rewritten synchronized transaction.

2. The recording system of claim 1, wherein said transactions comprise compressed information, and said provided data set information tables comprise uncompressed information, such that, in a read recovery of said partially filled data set and said succeeding data set, said written synchronized transaction is read and decompressed from said partially filled data set, said rewritten synchronized transaction of said succeeding data set is skipped, and said appended synchronized transaction is read and decompressed from said succeeding data set.

3. A recording system for a magnetic tape drive, said magnetic tape drive having at least one motor for moving a magnetic tape longitudinally, said magnetic tape having a plurality of wraps;

said magnetic tape drive having at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor;

said magnetic tape drive for receiving data to be written to said magnetic tape, said recording system comprising;

at least one recording channel receiving said data to be written to said magnetic tape, said data in the form of transactions, said at least one recording channel for operating said at least one read/write head for writing transactions to said magnetic tape at said plurality of wraps; and

a controller operating said at least one motor, and said at least one recording channel, said controller;

detects a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

writes said synchronized transactions to at least one of said plurality of wraps of said magnetic tape as synchronized transactions, in the form of data sets, each data set having a data set information table;

provides, in said data set information table of each data set for said synchronized transactions, a number representing a thread for said synchronized transactions of said detected pattern;

provides, in said data set information table of each data set of said synchronized transactions, the status of said data set; and

provides, in said data set information table of each data set of said synchronized transactions, an identification of the wrap of the immediately succeeding data set of said synchronized transactions, if any.

4. A recording system for a magnetic tape drive, said magnetic tape drive having at least one motor for moving a magnetic tape longitudinally, said magnetic tape having a plurality of wraps;

said magnetic tape drive having at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor;

said magnetic tape drive for receiving data to be written to said magnetic tape, said recording system comprising;

at least one recording channel receiving said data to be written to said magnetic tape, said data in the form of transactions, and said at least one recording channel for operating said at least one read/write head for writing transactions to said magnetic tape at said plurality of wraps; and

a controller operating said at least one motor, and said at least one recording channel, said controller;

detects a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

writes said synchronized transactions to at least one of said plurality of wraps of said magnetic tape, in the form of work copy data sets, each work copy data set having a data set information table;

subsequently recursively writes said synchronized transactions to said magnetic tape in a sequence, in the form of data sets, each data set having a data set information table;

provides, in said data set information table of each said data set, a number representing a thread for said synchronized transactions of said detected pattern;

provides, in said data set information table of each said data set, the status of said data set;

provides, in said data set information table of each said data set, an identification of the wrap of the immediately succeeding said data set, if any; and

provides, in said data set information table of each said recursively written synchronized transaction data set, a backwards pointer to a longitudinal position on said magnetic tape of a work copy data set.

5. The recording system of claim 4, wherein said controller, provides said status of each said data set, identifying in said status, the last data set of said synchronized transactions written to a wrap of said magnetic tape;

identifying in said status, the last data set of said synchronized transactions written to said plurality of wraps of said magnetic tape; and

identifying in said status, the last data set of said synchronized transactions subsequently recursively written to said magnetic tape.

6. The recording system of claim 5, wherein said controller initially writes at least one data set of said synchronized transactions of said pattern to said magnetic tape as a normal wrap data set before switching to a work copy wrap, said data set having a data set information table, and wherein said controller additionally provides said status of said normal wrap data set in said data set information table, identifying in said status, the last said normal wrap data set;

and wherein said a number representing a thread for said synchronized transactions of said detected pattern, comprises the write pass number of the last data set having a transaction of said pattern written to said magnetic tape as a normal wrap data set, and before said synchronized transaction data sets are written.

7. A recording system for a magnetic tape drive, said magnetic tape drive having at least one motor for moving a magnetic tape longitudinally, said magnetic tape having a plurality of wraps;

said magnetic tape drive having at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor;

said magnetic tape drive for receiving data to be written to said magnetic tape, said recording system comprising;

at least one recording channel receiving said data to be written to said magnetic tape, said data in the form of transactions, and said at least one recording channel for operating said at least one read/write head for writing transactions to said magnetic tape at said plurality of wraps; and

a controller operating said at least one motor, and said at least one recording channel, said controller;

detects a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

writes said synchronized transactions to at least one of said plurality of wraps of said magnetic tape as written synchronized transactions, in the form of data sets, each data set having a data set information table;

in the event one of said written synchronized transactions partially fills a data set, rewrites said synchronized transaction of said data set in a succeeding data set, appends a subsequent said synchronized transaction in said succeeding data set as an appended synchronized transaction; and

establishes a moving access point for said succeeding data set in said data set information table of said succeeding data set, said moving access point identifying said appended synchronized transaction, thereby skipping said rewritten synchronized transaction;

provides, in said data set information table of each said data set for said synchronized transactions, a number representing a thread for said synchronized transactions of said detected pattern;

provides, in said data set information table of each data set for said synchronized transactions, the status of said data set; and

provides, in said data set information table of each data set for said synchronized transactions, an identification of the wrap of the immediately succeeding data set of said synchronized transactions, if any.

8. A magnetic tape drive, comprising:

at least one motor for moving a magnetic tape longitudinally;

at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor;

at least one recording channel for receiving data to be written to magnetic tape, said data in the form of transactions, said at least one recording channel for operating said at least one read/write head for writing transactions to said magnetic tape; and

a controller operating said at least one motor, and said at least one recording channel, said controller;

detects a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

operates said at least one read/write head to access said magnetic tape and to write said synchronized transactions to said magnetic tape as written synchronized transactions, in the form of data sets, each data set having a data set information table;

in the event one of said written synchronized transactions partially fills a data set, rewrites said written synchronized transaction of said data set in a succeeding data set, appends a subsequent said synchronized transaction in said succeeding data set as an appended synchronized transaction; and

establishes a moving access point for said succeeding data set in said data set information table of said succeeding data set, said moving access point identifying said appended synchronized transaction, thereby skipping said rewritten synchronized transaction.

9. The magnetic tape drive of claim 8, wherein said transactions comprise compressed information, and said provided data set information tables comprise uncompressed information, such that, in a read recovery of said partially filled data set and said succeeding data set, said written synchronized transaction is read and decompressed from said partially filled data set, said rewritten synchronized transaction of said succeeding data set is skipped, and said appended synchronized transaction is read and decompressed from said succeeding data set.

10. A magnetic tape drive, comprising:

at least one motor for moving a magnetic tape longitudinally, said magnetic tape comprising a plurality of wraps;

at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor;

a wrap control system for accessing said wraps of said magnetic tape with said at least one read/write head;

at least one recording channel for receiving data to be written to said magnetic tape, said data in the form of transactions, said at least one recording channel for operating said at least one read/write head for writing transactions to said magnetic tape; and

a controller operating said at least one motor, said wrap control system, and said at least one recording channel, said controller;

detects a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

operates said wrap control system and said at least one read/write head to access at least one work copy wrap of said magnetic tape and to write said synchronized transactions of said detected pattern to said at least one work copy wrap of said magnetic tape, in the form of data sets, each data set having a data set information table;

provides, in said data set information table of each data set for said synchronized transactions, a number representing a thread for said synchronized transactions of said detected pattern;

provides, in said data set information table of each data set of said synchronized transactions, the status of said data set; and

provides, in said data set information table of each data set of said synchronized transactions, an identification of the wrap of the immediately succeeding data set of said synchronized transactions, if any.

11. A magnetic tape drive, comprising:

at least one motor for moving a magnetic tape longitudinally, said magnetic tape comprising a plurality of wraps;

at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor;

a wrap control system for accessing said wraps of said magnetic tape with said at least one read/write head;

at least one recording channel for receiving data to be written to said magnetic tape, said data in the form of transactions, said at least one recording channel for operating said at least one read/write head for writing transactions to said magnetic tape; and

a controller operating said at least one motor, said wrap control system, and said at least one recording channel, said controller;

detects a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

operates said wrap control system and said at least one read/write head to access at least one work copy wrap of said magnetic tape and to write said synchronized transactions of said detected pattern to said at least one work copy wrap of said magnetic tape, in the form of data sets, each data set having a data set information table;

subsequently operates said wrap control system and said at least one read/write head to access at least one normal wrap separate from said at least one work copy wrap, and to recursively write said synchronized transactions to said at least one normal wrap of said magnetic tape in a sequence, in the form of data sets, each data set having a data set information table;

provides, in said data set information table of each said data set, a number representing a thread for said synchronized transactions of said detected pattern;

provides, in said data set information table of each said data set, the status of said data set;

provides, in said data set information table of each said data set, an identification of the wrap of the immediately succeeding said data set, if any; and

provides, in said data set information table of each said recursively written synchronized transaction data set, a backwards pointer to a longitudinal position on said magnetic tape of a work copy data set.

12. The magnetic tape drive of claim 11, wherein said controller, provides said status of each said data set, identifying in said status, the last data set of said synchronized transactions written to a wrap of said magnetic tape;

identifying in said status, the last data set of said synchronized transactions written to said plurality of wraps of said magnetic tape; and

identifying in said status, the last data set of said synchronized transactions subsequently recursively written to said magnetic tape.

13. The magnetic tape drive of claim 12, wherein said controller initially writes at least one data set of said synchronized transactions of said pattern to said magnetic tape as a normal wrap data set before switching to a work copy wrap, said data set having a data set information table, and wherein said controller additionally provides said status of said normal wrap data set in said data set information table, identifying in said status, the last said normal wrap data set;

and wherein said a number representing a thread for said synchronized transactions of said detected pattern, comprises the write pass number of the last data set having a transaction of said pattern written to said magnetic tape as a normal wrap data set, and before said synchronized transaction data sets are written.

14. A magnetic tape drive, comprising:

at least one motor for moving a magnetic tape longitudinally, said magnetic tape comprising a plurality of wraps;

at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor;

a wrap control system for accessing said wraps of said magnetic tape with said at least one read/write head;

at least one recording channel for receiving data to be written to said magnetic tape, said data in the form of transactions, said at least one recording channel for operating said at least one read/write head for writing transactions to said magnetic tape; and

a controller operating said at least one motor, said wrap control system, and said at least one recording channel, said controller;

detects a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

operates said wrap control system and said at least one read/write head to access at least one work copy wrap of said magnetic tape and to write said synchronized transactions of said detected pattern to said at least one work copy wrap of said magnetic tape as written synchronized transactions, in the form of data sets, each data set having a data set information table;

in the event one of said written synchronized transactions partially fills a data set, rewrites said written synchronized transaction of said data set in a succeeding data set, appends a subsequent said synchronized transaction in said succeeding data set as an appended synchronized transaction; and

establishes a moving access point for said succeeding data set in said data set information table of said succeeding data set, said moving access point identifying said appended synchronized transaction, thereby skipping said rewritten synchronized transaction;

provides, in said data set information table of each said data set for said synchronized transactions, a number representing a thread for said synchronized transactions of said detected pattern;

provides, in said data set information table of each data set for said synchronized transactions, the status of said data set; and

provides, in said data set information table of each data set for said synchronized transactions, an identification of the wrap of the immediately succeeding data set of said synchronized transactions, if any.

15. A method for writing received synchronized data to magnetic tape, in a magnetic tape drive having at least one motor for moving said magnetic tape longitudinally, having at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor, and having at least one recording channel for operating said at least one read/write head for writing data to said magnetic tape, said data in the form of transactions, said method comprising the steps of:

detecting a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

writing said synchronized transactions to said magnetic tape as written synchronized transactions, in the form of data sets, each data set having a data set information table;

in the event one of said written synchronized transactions partially fills a data set, rewriting said synchronized transaction of said data set in a succeeding data set, appending a subsequent said synchronized transaction in said succeeding data set as an appended synchronized transaction; and

establishing a moving access point for said succeeding data set in said data set information table of said succeeding data set, said moving access point identifying said appended synchronized transaction, thereby skipping said rewritten synchronized transaction.

16. The method of claim 15, wherein said transactions comprise compressed information, and said provided data set information tables comprise uncompressed information, such that, in a read recovery of said partially filled data set and said succeeding data set, said written synchronized transaction is read and decompressed from said partially filled data set, said rewritten synchronized transaction of said succeeding data set is skipped, and said appended synchronized transaction is read and decompressed from said succeeding data set.

17. A method for writing received synchronized data to magnetic tape, said magnetic tape comprising a plurality of wraps, in a magnetic tape drive having at least one motor for moving said magnetic tape longitudinally, having at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor, having a wrap control system for accessing said wraps of said magnetic tape with said at least one read/write head, and having at least one recording channel for operating said at least one read/write head for writing data to said magnetic tape, said data in the form of transactions, said method comprising the steps of:

detecting a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

accessing at least one work copy wrap of said magnetic tape with said at least one read/write head;

writing said synchronized transactions of said detected pattern to said at least one work copy wrap of said magnetic tape, in the form of data sets, each data set having a data set information table;

providing, in said data set information table of each said data set, a number representing a thread for said synchronized transactions of said detected pattern;

providing, in said data set information table of each said data set, the status of said data set; and

providing, in said data set information table of each said data set, an identification of the wrap of the immediately succeeding said data set, if any.

18. A method for writing received synchronized data to magnetic tape, said magnetic tape comprising a plurality of wraps, in a magnetic tape drive having at least one motor for moving said magnetic tape longitudinally, having at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor, having a wrap control system for accessing said wraps of said magnetic tape with said at least one read/write head, and having at least one recording channel for operating said at least one read/write head for writing data to said magnetic tape, said data in the form of transactions, said method comprising the steps of:

detecting a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

accessing at least one work copy wrap of said magnetic tape with said at least one read/write head;

writing said synchronized transactions of said detected pattern to said at least one work copy wrap of said magnetic tape, in the form of data sets, each data set having a data set information table;

subsequently accessing at least one normal wrap of said magnetic tape separate from said at least one work copy wrap;

recursively writing said synchronized transactions to said at least one normal wrap of said magnetic tape in a sequence, in the form of data sets, each data set having a data set information table;

providing, in said data set information table of each said data set, a number representing a thread for said synchronized transactions of said detected pattern;

providing, in said data set information table of each said data set, the status of said data set;

providing, in said data set information table of each said data set, an identification of the wrap of the immediately succeeding said data set, if any; and

providing, in said data set information table of each said recursively written synchronized transaction data set, a backwards pointer to a longitudinal position on said magnetic tape of a work copy data set.

19. The method of claim 18, wherein said step of providing said status of each said data set, comprises identifying in said status, the last data set of said synchronized transactions written to a wrap of said magnetic tape;

identifying in said status, the last data set of said synchronized transactions written to said plurality of wraps of said magnetic tape; and

identifying in said status, the last data set of said synchronized transactions subsequently recursively written to said magnetic tape.

20. The method of claim 19, additionally comprising the steps of:

initially writing at least one data set of said synchronized transactions of said pattern to said magnetic tape as a normal wrap data set before switching to a work copy wrap, said data set having a data set information table; and

providing said status of said normal wrap data set in said data set information table, identifying in said status, the last said normal wrap data set; and

wherein said step of providing a number representing a thread for said synchronized transactions of said detected pattern, comprises providing the write pass number of the last data set having a transaction of said pattern written to said magnetic tape as a normal wrap data set, and before said synchronized transaction data sets are written.

21. A method for writing received synchronized data to magnetic tape, said magnetic tape comprising a plurality of wraps, in a magnetic tape drive having at least one motor for moving said magnetic tape longitudinally, having at least one read/write head for reading from and for writing to said magnetic tape while said magnetic tape is moved longitudinally by said at least one motor, having a wrap control system for accessing said wraps of said magnetic tape with said at least one read/write head, and having at least one recording channel for operating said at least one read/write head for writing data to said magnetic tape, said data in the form of transactions, said method comprising the steps of:

detecting a pattern of synchronizing events for writing said transactions to said magnetic tape as synchronized transactions;

accessing at least one work copy wrap of said magnetic tape with said at least one read/write head;

writing said synchronized transactions to said at least one work copy wrap of said magnetic tape as written synchronized transactions, in the form of data sets, each data set having a data set information table;

in the event one of said written synchronized transactions partially fills a data set, rewriting said synchronized transaction of said data set in a succeeding data set, appending a subsequent said synchronized transaction in said succeeding data set as an appended synchronized transaction; and

establishing a moving access point for said succeeding data set in said data set information table of said succeeding data set, said moving access point identifying said appended synchronized transaction, thereby skipping said rewritten synchronized transaction;

providing, in said data set information table of each said data set, a number representing a thread for said synchronized transactions of said detected pattern;

providing, in said data set information table of each said data set, the status of said data set; and

providing, in said data set information table of each said data set, an identification of the wrap of the immediately succeeding said data set, if any.