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CLOCK: [2023-06-14 Wed 16:41:52]--[2023-06-14 Wed 16:49:14] => 00:07:22 CLOCK: [2023-06-14 Wed 16:41:52]--[2023-06-14 Wed 16:49:14] => 00:07:22
:END: :END:
- DONE Deadlock and how it can be resolved. #flashcard - DONE Deadlock and how it can be resolved. #flashcard
id:: 64841da4-d8ce-46f5-bbe6-4dee620cde75
- A deadlock is a situation in which two or more transactions are unable - A deadlock is a situation in which two or more transactions are unable
to proceed because each is waiting for a resource held by the other, to proceed because each is waiting for a resource held by the other,
resulting in a circular dependency and a system halt. It is a form of resulting in a circular dependency and a system halt. It is a form of
@ -1017,29 +1018,39 @@
database management systems. database management systems.
- Example: - Example:
- Cascading rollback #flashcard - Cascading rollback #flashcard
id:: 64897f0b-dda6-4cc3-a9c3-cf630bcb0658
- Cascading Rollback: a transaction (T1) causes a - Cascading Rollback: a transaction (T1) causes a
failure and a rollback must be performed. Other failure and a rollback must be performed. Other
transactions dependent on T1's actions must also transactions dependent on T1's actions must also
be rollbacked, thus causing a cascading effect. be rollbacked, thus causing a cascading effect.
- One transaction's failure causes many to fail. - One transaction's failure causes many to fail.
- DONE ACID (Atomicity, Consistency, Isolation, Durability): A set of properties that guarantee the reliability and integrity of database transactions. #flashcard - DONE ACID (Atomicity, Consistency, Isolation, Durability): A set of properties that guarantee the reliability and integrity of database transactions. #flashcard
id:: 64841da4-0055-4d34-9f61-1402ff068ec7
collapsed:: true collapsed:: true
- Atomicity: :-> The property that ensures a transaction is treated as a single, indivisible unit of work. It either executes all its operations successfully or rolls back to the initial state if any operation fails. - Atomicity: :-> The property that ensures a transaction is treated as a single, indivisible unit of work. It either executes all its operations successfully or rolls back to the initial state if any operation fails.
id:: 64841d38-4ea9-4b76-8585-8b9de23915da
- Consistency: :-> The property that ensures a transaction transforms the database from one consistent state to another consistent state. It maintains data integrity and adheres to defined business rules. - Consistency: :-> The property that ensures a transaction transforms the database from one consistent state to another consistent state. It maintains data integrity and adheres to defined business rules.
id:: 64841d38-2854-4dfb-8f21-0013fca66a0a
- Isolation: :-> The property that ensures concurrent transactions do not interfere with each other. Each transaction operates in isolation until it completes, preventing interference or conflicts. - Isolation: :-> The property that ensures concurrent transactions do not interfere with each other. Each transaction operates in isolation until it completes, preventing interference or conflicts.
id:: 64841d38-fd2b-435e-bd45-3bf487a74b6f
- Durability: :-> The property that ensures committed changes made by a transaction are permanently saved and will survive any subsequent system failures or crashes. - Durability: :-> The property that ensures committed changes made by a transaction are permanently saved and will survive any subsequent system failures or crashes.
id:: 64841d38-950c-431e-8f28-ece98e230554
- DONE Concurrency control - DONE Concurrency control
- DONE Meaning of serialisability. #flashcard - DONE Meaning of serialisability. #flashcard
id:: 648428e1-5136-4d15-97c0-12087085b47f
- The objective of serialisability is to find nonserial schedules that are equivalent to some serial schedule. Such a schedule is called serialisable. - The objective of serialisability is to find nonserial schedules that are equivalent to some serial schedule. Such a schedule is called serialisable.
- DONE How locking can ensure serialisability. #flashcard - DONE How locking can ensure serialisability. #flashcard
id:: 64841da4-8812-405f-b49a-69eec9a069d2
- Locking achieves serializability by using locks to control access to - Locking achieves serializability by using locks to control access to
shared resources (e.g., database objects like tables or rows) and shared resources (e.g., database objects like tables or rows) and
prevent conflicts between concurrent transactions. prevent conflicts between concurrent transactions.
- DONE 2PL #flashcard - DONE 2PL #flashcard
id:: 64841da4-eab4-40db-819f-249fe1437250
- In the 2PL protocol, transactions acquire and release locks on database - In the 2PL protocol, transactions acquire and release locks on database
objects (e.g., tables, rows) in two distinct phases: the growing phase objects (e.g., tables, rows) in two distinct phases: the growing phase
and the shrinking phase. and the shrinking phase.
- DONE How timestamping can ensure serialisability. #flashcard - DONE How timestamping can ensure serialisability. #flashcard
id:: 64842000-07a7-4439-8ce6-7789e0a3358d
- By using transaction timestamps and enforcing the read and write - By using transaction timestamps and enforcing the read and write
validation checks, concurrency control mechanisms can ensure that validation checks, concurrency control mechanisms can ensure that
transactions are executed in a way that maintains data consistency and transactions are executed in a way that maintains data consistency and
@ -1054,6 +1065,7 @@
- User mistakes. - User mistakes.
- Sabotage. - Sabotage.
- DONE Purpose of transaction log file. #flashcard - DONE Purpose of transaction log file. #flashcard
id:: 64841f8f-5a9e-4f22-8f51-47931937998a
- Contains information about all updates to - Contains information about all updates to
database: database:
- Transaction records. - Transaction records.
@ -1061,12 +1073,14 @@
- Often used for other purposes (for example, auditing). - Often used for other purposes (for example, auditing).
- For autiding - For autiding
- DONE Purpose of checkpointing. #flashcard - DONE Purpose of checkpointing. #flashcard
id:: 64841f91-1d24-49f6-9f83-7c8b565c647f
- When failure occurs, redo all transactions that - When failure occurs, redo all transactions that
committed since the checkpoint and undo all committed since the checkpoint and undo all
transactions active at time of crash. transactions active at time of crash.
- DONE Normalization - DONE Normalization
background-color:: yellow background-color:: yellow
- DONE Functional dependencies [g4g](https://www.geeksforgeeks.org/types-of-functional-dependencies-in-dbms/) #flashcard - DONE Functional dependencies [g4g](https://www.geeksforgeeks.org/types-of-functional-dependencies-in-dbms/) #flashcard
id:: 648428e1-e704-4e23-941d-af9833de6f93
- In a relational database management, functional dependency is a concept - In a relational database management, functional dependency is a concept
that specifies the relationship between two sets of attributes where one that specifies the relationship between two sets of attributes where one
attribute determines the value of another attribute. It is denoted as **X → Y**, where the attribute set on the left side of the arrow, **X** is called **Determinant** , and **Y** is called the **Dependent**. attribute determines the value of another attribute. It is denoted as **X → Y**, where the attribute set on the left side of the arrow, **X** is called **Determinant** , and **Y** is called the **Dependent**.
@ -1076,32 +1090,42 @@
:END: :END:
- DONE kinds of NF [tutorial](https://www.geeksforgeeks.org/normal-forms-in-dbms/) - DONE kinds of NF [tutorial](https://www.geeksforgeeks.org/normal-forms-in-dbms/)
- First Normal Form (1NF): :-> This is the most basic level of - First Normal Form (1NF): :-> This is the most basic level of
id:: 648974ba-7334-4e73-a0ae-6b8fc6ec99ab
normalization. In 1NF, each table cell should contain _only a single value, and each column should have a unique name_. The first normal form helps to eliminate duplicate data and simplify queries. normalization. In 1NF, each table cell should contain _only a single value, and each column should have a unique name_. The first normal form helps to eliminate duplicate data and simplify queries.
- Second Normal Form (2NF): :-> 2NF eliminates redundant data by requiring that each _non-key attribute_ be dependent on the primary key. This means that _each column should be directly related to the primary key_, and not to other - Second Normal Form (2NF): :-> 2NF eliminates redundant data by requiring that each _non-key attribute_ be dependent on the primary key. This means that _each column should be directly related to the primary key_, and not to other
id:: 648974ba-cc9e-4cdf-a312-3af1bcab23f2
columns. columns.
- Third Normal Form (3NF): :-> 3NF builds on 2NF by requiring - Third Normal Form (3NF): :-> 3NF builds on 2NF by requiring
id:: 648974ba-f325-450e-aede-9a7d92bcf888
that _all non-key attributes are independent of each other._ This means that each column should be directly related to the primary key, and not to any other columns in the same table. that _all non-key attributes are independent of each other._ This means that each column should be directly related to the primary key, and not to any other columns in the same table.
- Boyce-Codd Normal Form (BCNF): :-> BCNF is a stricter form of 3NF that ensures that each determinant in a table is a candidate key. In other words, BCNF ensures that _each non-key attribute is dependent only on the candidate key._ - Boyce-Codd Normal Form (BCNF): :-> BCNF is a stricter form of 3NF that ensures that each determinant in a table is a candidate key. In other words, BCNF ensures that _each non-key attribute is dependent only on the candidate key._
id:: 64842000-c15a-4b8f-95c3-d6c6e49e4af0
- Fourth Normal Form (4NF): 4NF is a further refinement of BCNF that ensures that _a table does not contain any multi-valued dependencies._ - Fourth Normal Form (4NF): 4NF is a further refinement of BCNF that ensures that _a table does not contain any multi-valued dependencies._
- Fifth Normal Form (5NF): 5NF is the highest level of normalization and involves decomposing a table into smaller tables to _remove data redundancy and improve data integrity._ - Fifth Normal Form (5NF): 5NF is the highest level of normalization and involves decomposing a table into smaller tables to _remove data redundancy and improve data integrity._
- LATER Block 4 - LATER Block 4
- DONE Distributed DBMS - DONE Distributed DBMS
- DONE client server arch #flashcard - DONE client server arch #flashcard
id:: 648974ba-9c11-4816-9d5e-0623dc4d4d45
- Computers (client) connected over wired or wireless local area network (LAN) - Computers (client) connected over wired or wireless local area network (LAN)
- The database itself and the DBMS are stored on a central device called the database server, which is also connected to the network. - The database itself and the DBMS are stored on a central device called the database server, which is also connected to the network.
- Distributed Database #flashcard - Distributed Database #flashcard
id:: 648974ba-b13a-4f3f-8409-ea02b5ef5894
- A logically interrelated collection of shared data (and a description of this data), physically spread over a computer network. - A logically interrelated collection of shared data (and a description of this data), physically spread over a computer network.
- Distributed DBMS #flashcard - Distributed DBMS #flashcard
id:: 648974ba-997c-4f43-b2d6-d972cfc23d36
- Software system that permits the management of the distributed database and makes the distribution transparent to users. - Software system that permits the management of the distributed database and makes the distribution transparent to users.
- the key issues #flashcard - the key issues #flashcard
id:: 648974ba-4c63-4215-b420-d537c2a93675
- Fragmentation - Fragmentation
- Allocation - Allocation
- Replication - Replication
- importance and different types of fragmentation #flashcard - importance and different types of fragmentation #flashcard
id:: 648974ba-07aa-4c51-aa70-1c8dfb4570e7
- Horizontal - Horizontal
- Vertical - Vertical
- Mixed - Mixed
- different types of transparency #flashcard - different types of transparency #flashcard
id:: 648974ba-6db5-4d3a-af62-1695e7c3a9b7
- Distribution Transparency: The database feels as a single, logical entity - Distribution Transparency: The database feels as a single, logical entity
- Transaction Transparency: Ensures that all distributed transactions maintain distributed database’s integrity and consistency. - Transaction Transparency: Ensures that all distributed transactions maintain distributed database’s integrity and consistency.
- Performance Transparency: must perform as if it were a centralized DBMS. - Performance Transparency: must perform as if it were a centralized DBMS.