High Resolution Tape Directory Recovery via End of Data Set Overwriting
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Solution Overview
Problem
High Resolution Tape Directory (HRTD) cannot be recorded in the non-volatile memory of tape cartridges due to its large size, leading to difficulties in retrieving and maintaining the directory, especially when tape media conditions deteriorate, resulting in long recovery times and potential loss of data.
Innovation Solution
The HRTD is written at the End of Data Set (EOD) location next to user data, allowing it to be overwritten and stored with an incremented Tape Write Pass, enabling recovery from the EOD even if the original EOD is overwritten, thus ensuring the directory's integrity and reducing recovery time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If HRTD is stored in non-volatile memory of tape cartridge, then directory retrieval is simplified, but the large size of HRTD exceeds the storage capacity of cartridge memory
Solution Approach 1:
The HRTD is extracted from the cartridge memory storage location and placed instead at the End of Data Set (EOD) on the tape medium itself. This extraction resolves the capacity conflict by utilizing tape space rather than limited cartridge memory, while still enabling directory retrieval through the EOD structure.
Solution Approach 2:
The directory storage is moved from the two-dimensional cartridge memory space to the linear tape dimension at the EOD location. This dimensional transition allows the large HRTD to be stored by utilizing the extended linear capacity of the tape medium rather than the constrained cartridge memory space.
2Quantity of substance
If HRTD is stored on tape at EOD location, then storage capacity is sufficient, but tape media deterioration and overwriting risks increase
Solution Approach 1:
A new EOD is written at a position next to the end longitudinal position of the previous EOD before the old EOD is completely overwritten. This preliminary action ensures that the HRTD is captured and stored in the new EOD location while maintaining the ability to retrieve it, preventing complete loss from media deterioration or overwriting.
Solution Approach 2:
The system creates a buffer zone by writing the new EOD adjacent to rather than directly over the old EOD. This cushioning approach provides a safety margin that protects against complete data loss, allowing recovery from the new EOD location even if the old EOD becomes corrupted or is accidentally overwritten.
3Productivity
If new user data set is appended by overwriting EOD, then tape space is utilized efficiently, but HRTD information may be lost
Solution Approach 1:
The new EOD containing the updated HRTD is written at the position next to the end LPOS of the previous EOD before the append operation proceeds. This preliminary writing ensures that the directory information is preserved in the new EOD location, allowing efficient tape space utilization through overwriting while preventing information loss through the new EOD's HRTD storage.
Data Source
AI summary
An End of Data Set (EOD) including a High Resolution Tape Directory (HRTD) is written at a position next to a last written user data set on a tape. When appending a new user data set, the new user data set is written starting from a position next to an end longitudinal position (LPOS) of the EOD to generate an overwritten EOD.