Magnetic Tape Care, Storage, and Error Recovery.

Fuente: ERIC Institute of Education Sciences

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Bibliographic Details
Main Author:	Schenck, Thomas
Format:	Recurso educativo Open Access
Language:	en
Published:	1984
Subjects:	Computer Storage Devices Information Storage Magnetic Tapes Preservation
Online Access:	Acceder al recurso
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_version_	1867181498145177600
author	Schenck, Thomas
author_facet	Schenck, Thomas Schenck, Thomas
collection	Education Resources Information Center
contents	Magnetic Tape Care, Storage, and Error Recovery. Schenck, Thomas Computer Storage Devices Information Storage Magnetic Tapes Preservation Explains format of data on magnetic tape and process of reading and writing data to tape, and discusses sources of tape errors (physically damaged tape, unclean tape, magnetic alteration of data on tape, unclean or defective tape drive); correcting and/or bypassing tape errors; and care, storage, and shipment of tapes. (EJS)
format	Recurso educativo Open Access
id	eric_EJ314059
institution	ERIC Institute of Education Sciences
language	en
publishDate	1984
record_format	eric
spellingShingle	Magnetic Tape Care, Storage, and Error Recovery. Schenck, Thomas Computer Storage Devices Information Storage Magnetic Tapes Preservation Magnetic Tape Care, Storage, and Error Recovery. Schenck, Thomas Computer Storage Devices Information Storage Magnetic Tapes Preservation Explains format of data on magnetic tape and process of reading and writing data to tape, and discusses sources of tape errors (physically damaged tape, unclean tape, magnetic alteration of data on tape, unclean or defective tape drive); correcting and/or bypassing tape errors; and care, storage, and shipment of tapes. (EJS)
title	Magnetic Tape Care, Storage, and Error Recovery.
topic	Computer Storage Devices Information Storage Magnetic Tapes Preservation
url	https://eric.ed.gov/?id=EJ314059

if (filemtime($filename) + $maxlifetime < time()) { unlink($filename); $count++; } } return $count; } /** * A function that is called internally when session data is to be saved. * * @param string $sessId The current session ID * @param string $data The session data to write * * @return bool */ protected function saveSession($sessId, $data): bool { $sessFile = $this->path . '/sess_' . $sessId; if ($handle = fopen($sessFile, 'w')) { $return = false; // Lock the file for exclusive access to avoid issues with multiple // processes writing session simultaneously: if (flock($handle, LOCK_EX)) { $return = fwrite($handle, $data); // Make sure that there's no trailing data by truncating the file to // the correct length: ftruncate($handle, strlen($data)); fflush($handle); flock($handle, LOCK_UN); } fclose($handle); if ($return !== false) { return true; } } // If we got this far, something went wrong with the file output... // It is tempting to throw an exception here, but this code is called // outside of the context of exception handling, so all we can do is // echo a message.

// Anecdotal testing Today and Yesterday seems to indicate destroy() // is called by the garbage collector and everything is good. // Something to keep in mind though. return 0; } /** * Write function that is called when session data is to be saved. * * @param string $sessId The current session ID * @param string $data The session data to write * * @return bool */ public function write($sessId, $data): bool { if ($this->writesDisabled) { return true; } return $this->saveSession($sessId, $data); } /** * A function that is called internally when session data is to be saved. * * @param string $sessId The current session ID * @param string $data The session data to write * * @return bool */ abstract protected function saveSession($sessId, $data): bool; }

* * @return void */ public function writeClose() { // The assumption is that we're using PHP's ext/session. // session_write_close() will actually overwrite $_SESSION with an // empty array on completion -- which leads to a mismatch between what // is in the storage object and $_SESSION. To get around this, we // temporarily reset $_SESSION to an array, and then re-link it to // the storage object. // // Additionally, while you _can_ write to $_SESSION following a // session_write_close() operation, no changes made to it will be // flushed to the session handler. As such, we now mark the storage // object isImmutable. $storage = $this->getStorage(); if (! $storage->isImmutable()) { $_SESSION = $storage->toArray(true); session_write_close(); $storage->fromArray($_SESSION); $storage->markImmutable(); } } /** * Attempt to set the session name * * If the session has already been started, or if the name provided fails * validation, an exception will be raised. * * @param string $name * @return SessionManager * @throws Exception\InvalidArgumentException */ public function setName($name) { if ($this->sessionExists()) { throw new Exception\InvalidArgumentException( 'Cannot set session name after a session has already started'

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