OBIEE Isolation Levels in the Physical Layer

   
Committed Read

1) Locks are held while the data is read to avoid dirty reads. Data can be changed before the transaction ends with that connection.
2) Allows to insert new records and allows to update the records that a transaction isusing and would reflect only after commit, In other words data can be changed before end of transaction resulting in non repeatable reads.

 
Dirty Read

1) Locking. Can read uncommitted or dirty data, change values in data during read process in a transaction. Least restrictive of all types.
2) With this option it is possible to read uncommitted data and have rows appear and disappear before end of transaction
 
Repeatable Read

1) Places locks on all data used in a query so that nobody can update the data. However new rows can be inserted by other users but will be available in later reads in the current transaction.
2) Allows to insert new records and places the locks on the al the data that is used inthe query to prevent anybody else updating the data.

   
Serialization

1)Places a range lock on data set preventing other users to insert or update the rows in data set until the transaction is complete. Most restrictive of all.
2) Locks the dataset and does not allow to insert or update the data set until the transaction is complete.

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