It so happens that the transaction fails to execute until completion owing to software issues, hardware problems, or system crash. In such a situation, the failed transaction is rolled back by the rollback operation. However, another transaction may have utilized the value yielded by the failed transaction. Then that transaction will have to be rolled … Read more
Conflict Serializable Schedule When non-conflicting operations swap and transform into a serial schedule, the process is called conflict serializability. Also, when the schedule is conflict equivalent, then only it is conflict serializable. Operations of Conflicting The operations are conflicting in the following conditions: Both are from different transactions. Both contain the same data. Both … Read more
Checkpoint When all the old logs are deleted from the system and stored permanently in the storage disk, the mechanism is called checkpoint. When the execution of the transaction takes place, the checkpoints are marked acting as a bookmark. After the execution, it creates log files. When the file reaches the checkpoint, the transaction status … Read more
Timestamp Ordering Protocol The timestamp ordering protocol is helpful in ordering transactions according to their timestamps. The ascending order of the creation of transaction is called the order of transaction. The older transaction is executed first due to high priority. The protocol uses time of system or logical counter to determine transaction timestamp. At the … Read more
Indexed sequential access method is the organization of file in an advanced sequential manner. A primary key is used in this method to store records in the file. Also, it generates an index value, and mapping is done with the record. This index stores the address of the file. If we use the index … Read more
Relational Model Concept Relational model refers to any table with rows and columns. Each row of the table is called a tuple, and each column has a name, also known as an attribute. Domain: It consists of some atomic values of a particular attribute. Attribute: It is the name given to a particular column in … Read more
Functional Dependency The relationship existing between any two attributes is called functional dependency. This kind of relationship is present between the non-key attribute and the primary key inside a table. Functional dependencies come in use for designing or redesign of a relational database which assists to remove redundancy (duplication of data), thus minimizing the chance … Read more
RELATIONAL CALCULUS Relation status is mainly non-procedural query language. The non-procedural query language means that the user has the concern with the various details related to the obtaining of the end results. The relational calculus let us know about what should do you; however, it doesn’t explain about how to do. Kinds of Relational … Read more
Integrity Constraints The Set of rules which is used to maintain the quality of information are known as integrity constraints. Integrity constraints make sure about data intersection, update and so on. Integrity constraints can be understood as a guard against unintentional damage to the database. Different types of Integrity Constraints Domain Constraint The Definition … Read more
Join Operations Related tuples are combined from different relations in join operations. This holds valid only if a given join condition is met. Join operations are denoted by ⋈. Example EMPLOYEE Emp_Code Emp _Name 101 Jai 102 Mahesh 103 Vishal SALARY Emp_Code Emp _Name 101 90000 102 130000 103 125000 Operation: (EMPLOYEE⋈SALARY) RESULT: … Read more