A method of updating a sequential file by merging it with an amendment file and writing the resultant version to a different storage device than the one used to hold the preupdated file. It is performed sequentially with the key of each record in the file being updated checked against the keys of the amendment file to locate matches and keys not included in the sequence. Where no match is found, the record is copied to the new location. Where a match is found, the record in the amendment file is written to the new location. If a record in the amendment file has a key that is not represented in the file being updated, it is written to the new location in its correct sequence. Update by copy has the advantage of retaining the preupdated version, of being able to accommodate variable length records, and providing for easy insertion of “missing” records without the need to leave unused space for them.; 一種更新順序文件的方法.它利用一個(gè)修改文件與原順序文件進(jìn)行合并，合并的結(jié)果并不取代原文件，而是寫到另一存儲(chǔ)設(shè)備上，也就是順序地使 用原文件中的每個(gè)記錄的鍵與修改文件中相應(yīng)的鍵進(jìn)行比較，以找出匹配的和沒有的鍵，當(dāng) 兩者不同時(shí)，將原文件的記錄拷貝到新的位置； 當(dāng)兩者相同時(shí)，則把修改文件中的記錄寫 到新的位置.如果在修改文件中的某一記錄鍵在原文件中沒有表示出來，那么就將修改文件 中的記錄以修改次序?qū)懙叫碌奈恢?拷貝更新具有保留原文件以及能適當(dāng)變長(zhǎng)記錄等優(yōu)點(diǎn)， 并提供了容易插入“丟失”記錄的方法，而不需要再為“丟失”的記錄保留未使用的空間. 參閱update in situ