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| Multi-file Processing: Sequential Access |
1. What is the master file and transaction file?
Master file: A relatively permanent file that contains information used regularly; a file that must be updated and maintained.
Example: The inventory file.
Transaction file: A file that is retained for only a short time. It is a relatively temporary file that contains information that is used to update or maintain a master file.
Note : Master files and transaction files will be accessed sequentially.
2. What do you mean by sequential access and serial access?
Serial Access: Sequential access is a special case of serial access in which the records in the file are in order on one or more fields.
More information:
Sequential access is one form of serial access.
The value in a field in each record is called key field.
When the master and transaction files are in sequence on the same key field the matching process is much more efficient.
Serial access: Processing records in a file by starting with the first record and taking each succeeding record in turn.
3. What is the key field? Why do we use a key field?
The field or fields that are used to identify a record.
Key field used in:
i. Sorting a sequential file and in
ii. Retrieving records from a direct file.
4. What are the categories in file-processing activities?
File processing activities can be categorized as:
i. Maintaining
ii. Updating
iii. Referencing
5. How many types of forms media we will use for sequential files or master files?
We will use two types of forms media for sequential or master files.
i. Magnetic tape &
ii. Magnetic disk.
More information:
Magnetic tape is used today primarily as a medium for-
o backing up files that are stored on disc
o for long term storage of transaction data
o for transferring data &
o programs from one computer to another.
Tape is strictly a serial medium.
The computer is unable to go to directly to a specific record stored on tape.
6. What do you mean by maintaining?
Maintaining refers to the activities that change the number of records in a master file.
More information:
The most common maintenance activities are-
o Adding &
o Deleting records from a master file.
7. What do you mean by updating?
Changing the contents of records in a master file to keep it current without changing the number of records in the file.
8. What do you mean by referencing?
Retrieving information from a file without altering its contents.
9. Define the following Keywords:
• Activity rate: A measure of the relative number of records in a file that are altered in an updating
• Backing up: Providing a way to restore a master file in case the current version of the file can no longer be used.
• Grandfather- father- son backup: A technique for backing up master files stored on magnetic tape.
• Key field: The field or fields that are use to identify a record. It is used in sorting a sequential file and in retrieving records from a direct file.
• Maintain: Processing with the purpose of keeping a master file current that change the number of records in a file. For example, adding or deleting records.
• Master file: A relatively permanent file that contains information used regularly; a file that must be updated and maintained.
• Piggyback file: A file to which records are added by placing them after the records already in file.
• Referencing: Retrieving information from a file without altering its content.
• Sequential access: A special case of serial access in which the records in the file are in order on one or more fields.
• Serial access: Processing records in a file by starting with the first record and taking two alternatives for processing.
• Transaction file: A relatively temporary file that contains information that is used to update or maintain a master file.
• Updating: Changing the contents of records in a master file to keep it current without changing the number of record in the file.
• Volatility rate: A measure of the relative amount of change in the number of records in a master file.
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