OpenEdge Data Management: DataServer for Microsoft SQL Server

Transactions
Transactions
With DataServer operations, a MS SQL Server data source handles its own transaction roll back
and recovery operations. However, the OpenEdge transaction scoping rules apply: a transaction
ends when the code exits the outermost block that performs an update. With the DataServer,
ABL performs as follows:
• Sends a COMMIT to the data source, when a transaction that updates a MS SQL Server data
source ends successfully.c
• Sends a ROLLBACK to the data source if you interrupt the transaction.
See OpenEdge Getting Started: ABL Essentials for details on how ABL handles transactions
and error conditions.
Transaction scoping and buffer management
The DataServer and an OpenEdge database hold locks differently at transaction boundaries. The
OpenEdge database will hold a lock past the transaction boundary where the DataServer will
not. This causes different behavior in the use of buffers. Consider the following example:
DEFINE BUFFER st_buf1 FOR state.
DEFINE BUFFER st_buf2 FOR state.
DO TRANSACTION: /* Transaction 1 */
FIND st_buf1 WHERE st_buf1.state EQ "NH" EXCLUSIVE-LOCK.
DISPLAY st_buf1.state-name. /* state-name = "New Hampshire" */
END.
/* During this pause, state-name is changed from "New Hampshire" to "Granite
State" by an external user */
PAUSE MESSAGE " state.state-name ".
DO TRANSACTION: /* Transaction 2 */
FIND st_buf2 WHERE st_buf2.state EQ "NH" EXCLUSIVE-LOCK.
DISPLAY st_buf1.state-name st_buf2.state-name.
END.
Executing the above code against an OpenEdge database will downgrade the EXCLUSIVE-LOCK
in Transaction 1 to a SHARE-LOCK. This occurs at the end of Transaction 1 and remains in effect
at the time of the PAUSE statement and prior to the start of Transaction 2. This SHARE-LOCK
prevents another user from modifying the state-name value between the transactions. As an
optimization, when Transaction 2 is executed, the client does not refresh the st_buf1 buffer
since the SHARE-LOCK prevented its contents from becoming stale between transactions. Also,
since st_buf2 will have the same data integrity as st_buf1, they share the same buffer content.
2–43