Browse Prior Art Database

A method of fast access to data at the beginning of tape

IP.com Disclosure Number: IPCOM000012479D
Original Publication Date: 2003-May-12
Included in the Prior Art Database: 2003-May-12
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Abstract

Disclosed is a method to provide a first access to data which is written at the beginning of a tape medium and which contains necessary information to control or maintain the tape. The data is written in a primary restricted region of the tape, or unrestricted full region if there is some medium damage in the primary region. Necessary information about the written data in the tape is saved in the tape cartridge memory, and it is used at reading the data from the tape.

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A method of fast access to data at the beginning of tape

Problem

    Tape medium possibly requires housekeeping data in order to control or maintain the tape. If the size of the data is over the capacity of the cartridge memory (CM), all or part of the data should be stored in the tape medium itself. In such case, due to the data necessity, it is stored in a prior region of user data region, and it should be read earlier than the user data when the cartridge is loaded.

    The CM contains the landmarks information of the tape such as positions of user data area and housekeeping data area. The landmark information should be verified with the actual tape medium earlier than the housekeeping data as well as the user data, when the tape cartridge is loaded. After that, the tape is ready to use from a host PC.

    If the verified position is nearly equal to the beginning position of the housekeeping area, rewind to the beginning position is required as shown in Fig. 1, because there is some delay to complete the verification and it goes past the beginning position. The rewind wastes time so that it makes ready-time be worse.

Tape Head

Housekeeping data area

Landmark verification

decel. accel. to rewind

Wind/Rewind tape

ready-time Tape motion

Beginning position End positionof housekeeping areaof housekeeping area

User data area

Rewind makes ready-time be worse

time

Figure 1: Tape motion to read housekeeping data after loaded

Solution
1. Define primary and secondary regions for housekeeping data Define the region between the verification completed position and the end position of housekeeping area as the primary restricted region...