TMF Introduction (G06.24+)

TMF Application Programming

HP NonStop Transaction Management Facility (TMF) Introduction—522414-001

5-5

Accessing SQL Data

The NonStop SQL interface to TMF is implicit through the SQL data manipulation

statements SELECT, FETCH, DELETE, INSERT, and UPDATE. The application

selects the level of isolation. The locks to provide the selected isolation are

subsequently managed by TMF and the file system.

Applications can access a NonStop SQL database by using SQL statements

embedded in host language programs, including C, C++, COBOL85, and TAL.

The following example shows a cursor that accesses data from the PARTS table and

declares the intention of updating the data. (A cursor is a mechanism through which a

program retrieves a set of rows defined by the SELECT statement.)

EXEC SQL DECLARE list_by_partdesc_cursor CURSOR FOR

SELECT partnum, partdesc, price, qty_available

FROM sales.parts

WHERE (partdesc = :partdesc OF parts)

SERIALIZABLE ACCESS

FOR UPDATE OF PARTDESC, PRICE, QTY_AVAILABLE

END-EXEC.

After defining the set of rows, the program can retrieve them one-by-one and perform

update or delete operations on them; the program processes the cursor like a

sequential file.

The row in which the cursor is currently located is locked for exclusive access because

the FOR UPDATE clause was specified. As the program accesses rows through the

cursor, the rows remain locked until the transaction commits.

If this cursor were defined without the FOR UPDATE clause, the stable access option

would cause only the row in which the cursor is currently located to be locked with a

shared lock. The lock would be released when the next row becomes the current

position.

If this cursor were defined without the FOR UPDATE clause but with repeatable

access, all rows accessed through the cursor would remain locked until the transaction

commits.

Accessing Enscribe Data

Access to an Enscribe database is achieved either through programming language

statements or, for some languages, through calls to the system procedures for the

NonStop Kernel operating system. When applications access audited Enscribe files,

TMF automatically manages their transactions and data locking.

Standard language input/output provides access to Enscribe data for these languages:

COBOL, COBOL85, and FORTRAN. TACL has a built-in function, #REQUESTER,

that provides for reading and writing to Enscribe files.

System procedure calls provide access to Enscribe data for these languages: C, C++,

and TAL.