AutoTMF Software User's Guide (Update 12)

Configuring Automatic Transaction Processing

HP NonStop AutoTMF Software User’s Guide—429952-014

4-9

Audited File Renaming

Attempts to rename a file while the file is audited are rejected by the file system with an

error. Each audit record contains the name of the disk file being updated, so renaming

a file can make backout operations fail.

NonStop AutoTMF software can rename audited files by performing a complex series

of open, close, and alter operations. A file that is opened by other processes cannot be

renamed.

Null Record Handling (Entry-Sequenced Files)

Records can be inserted into an entry-sequenced file but they cannot be updated.

If the file is not audited, all inserted records are written to the file. Programs expect to

find a valid and complete record when reading the file.

If the file is audited and if a transaction is aborted, any non-committed record is

removed from the file and a null record (a zero-length record) is inserted in the non-

committed record’s place.

In many cases, a null record will cause problems for a non TMF-aware legacy program

because the program is not expecting to read zero-length records.

NonStop AutoTMF software can hide the existence of null records in an audited entry-

sequenced file by discarding the records instead of returning them to the programs.

Reading Through Locks

Normally a READ or READUPDATE operation requires that the record being accessed

is not currently locked. However, since the operation does not lock the record, nothing

prevents concurrent access to the same record by multiple processes.

NonStop AutoTMF software does not provide automatic transactions for non-locking

operations like READ. Normally, no transaction is required, but if a process performs a

READLOCK followed by READ operation on the same record, an error or deadlock

may occur.

To prevent errors and deadlocks, NonStop AutoTMF software automatically configures

each file open for read-through-locks mode. This mode has no effect on locking

operations such as READLOCK, only on non-locking access such as READ. You may

disable this configuration by altering the ATMFREADTHRULOCK global or by

specifying NO READTHRULOCK for a file set or program. If, however, a process

attempts a READ or READUPDATE on a file that has an active automatic transaction,

READTHRULOCK will always be set.

Note. The NonStop RDF product does not replicate the rename of an audited file on the

backup node because the rename operation is not audited.