Software Transaction Implementation

• Goals:

  • Non-transactional operations should be fast
  • Reads should be faster than writes
  • Minimal amount of object bloat

• Solution:

  • Use special FLAG value to indicate “location involved in a transaction”
  • Object points to a linked list of versions, containing values written by (in-progress, committed, or aborted) transactions
  • Semantic value of FLAGged field is: “value of the first version owned by a committed transaction on the version list”
  • Values which are “really” FLAG are handled with an escape mechanism (we call these “false flags”)

Notes: