AutoTMF Software User's Guide (Update 14)

Configuring Automatic Transaction Processing

HP NonStop AutoTMF Software User’s Guide—429952-016

4-12

Record-Level Transactions

Certain programs use a complex record-locking and record-unlocking sequence such

that at least one record is locked for long periods. AutoTMF will not commit an

automatic transaction until a program releases all locks obtained under the transaction.

If the processing contains no point where all locks are released, the automatic

transaction is never committed.

The resulting long-running transaction can cause lock contention, deadlocks, and,

eventually, a unilateral abort when the TMF AutoAbort time limit is reached.

Uncommitted updates could be lost. See the discussion in Unilateral Aborts on

page 4-16.

In such cases, you can configure AutoTMF to generate one automatic transaction for

each record lock and to commit each transaction as soon as the record is unlocked.

This approach increases the transactional activity but prevents the occurrence of long-

running transactions without changing the program’s locking behavior.

This feature is enabled by specifying the RECORDTX attribute on both the file on

which the locks are held and the accessing program. If RECORDTX is specified on

either the file or the program, but not on both, RECORDTX is ignored.

To implement RECORDTX, AutoTMF maintains a table of records locked and the

associated transaction for each lock. If the same record is locked multiple times, the

same transaction is used for each lock until the lock is released and the transaction is

committed.

Exceptions

Certain sequences of operations do not lend themselves to the generation of automatic

transactions for each record lock. In these cases, the RECORDTX attribute is not

supported and cannot be used:



If a program issues READLOCK (In COBOL, READ NEXT WITH LOCK) to read

records sequentially, AutoTMF cannot predict the key of the next record that will be

locked, so AutoTMF cannot identify which transaction to use if the same record is

locked more than once. As long as READLOCK is used to lock records that are not

already locked, READLOCK may be used with RECORDTX.



If a program does a LOCKFILE after locking two or more records, the file cannot

be locked unless the records are unlocked first. Otherwise, the same record could

be locked under more than one transaction, leading to internal deadlocks. If a

LOCKFILE operation that has more than one record lock is requested, the

LOCKFILE operation will be abended.



If a program issues READUPDATELOCK with positioning by a unique alternate

key, AutoTMF cannot predict the primary key of the record being locked, so

AutoTMF cannot identify which transaction to use if the same record is locked

more than once. As long as READUPDATELOCK is used to lock records that are

not already locked, READUPDATELOCK may be used with RECORDTX.