11.3. About REPEATABLE_READ

REPEATABLE_READ is one of two isolation modes available in JBoss Data Grid.

Traditionally, REPEATABLE_READ does not allow write operations while read operations are in progress, nor does it allow read operations when write operations occur. This prevents the "non-repeatable read" phenomenon, which occurs when a single transaction has two read operations on the same row but the retrieved values differ (possibly due to a write operating modifying the value between the two read operations).

JBoss Data Grid's REPEATABLE_READ isolation mode preserves the value of a row before a modification occurs. As a result, the "non-repeatable read" phenomenon is avoided because a second read operation on the same row retrieves the preserved value rather than the new modified value. As a result, the two values retrieved by the two read operations will always match, even if a write operation occurs between the two reads.