Table 3 Possible failures in each operation

Pack operation on fixed and variable length records

Concatenation of attributes of fields to compose a record

1. Overflow of record fields

2. Data of a record exceeds the length of the record

3. Null values to record fields

4. Data type mismatch between record fields and values

5. File cannot be opened for write operation

Unpack operation on fixed and variable length records

Extraction of attributes of fields of a record

1. Null value of a field

2. Type mismatch between target data type and field value

3. File not found

4. File cannot be opened for read operation

Search using relative record number (RRN)

Search an index file for a record whose RRN is same as a search key

1. Record not found

2. Invalid RRN

3. RRN exceeds maximum value

Primary index and Secondary index

Building primary and secondary indexes for a data file

1. Primary key constraint violation

2. Incorrect index record address

3. Invalid secondary key value

Balanced trees

Balanced trees to manipulate data records

1. Incorrect leaf node

2. Incorrect key index

3. Deletion of a key from empty node

Hashing

Generate a unique address to each data record to store it in a hash table

1. Multiple keys hash to the same address

2. Overflow of hash table

Storage compaction

Method to reuse memory reserved for data records which no more exist

1. Internal and external fragmentation