HP 3000 Manuals HP 3000 Manuals
Super Transactions
Silhouette handles super transactions exactly as it handles ordinary
database transactions. A super transaction is a logically connected
series of transactions spanning multiple databases or multiple database
paths. A typical super transaction consists of multiple DBBEGIN/DBEND
pairs each of which can contain multiple calls to TurboIMAGE routines.
Creating a Super Transaction
To create a super transaction, the user process identifies the records in
the logfile which form the transaction. Each DBBEGIN of the super
transaction must be called with a ten-byte unique text identifier flanked
by double asterisks. The identifier must have the form:
**..........**
The dots are replaced with a unique sequence of characters.
Figure 2-6 shows a sample of logfile records which includes a super
transaction.
____________________________________________________________________
| |
| Log record Contents |
| |
| . |
| . |
| 1 ADD1 |
| 2 DBBEGIN2 **STRANS1 ** |
| 3 ADD2 |
| 4 DBBEGIN3 **STRANS1 ** |
| 5 ADD3 |
| 6 DEL1 |
| 7 DEL3 |
| 8 DBEND3 (This END matches the BEGIN in record 4.)|
| 9 DEL2 |
| 10 UPDATE1 |
| 11 UPDATE2 |
| 12 DBEND2 (This END matches the BEGIN in record 2.)|
| 13 DEL1 |
| . |
| . |
____________________________________________________________________
Figure 2-6. Super Transaction Log File Record
The super transaction consists of the log records 2-5, 7-9, 11 and 12.
Records 1, 6, 10 and 13 are not part of the super transaction because
they are not part of a DBBEGIN/DBEND pair containing the unique super
transaction identifier.
>SWITCH With Super Transactions
If the primary system fails before record 12 is added to the logfile, the
>SWITCH command performs its normal function of removing incomplete
transactions from the database and removes all individual transactions
which form part of the super transaction. Records 2-5, 7-9, 11 and 12
are removed. Records 1, 6, 10 and 13 are not removed since they do not
leave the database in an inconsistent state. The listing produced by the
>SWITCH command includes super transactions. When the last complete
transaction performed by a user is a super transaction, the listing shows
the entire contents of that transaction since Silhouette considers it to
be one logical modification of the database. If the super transaction is
incomplete, the >SWITCH command listing shows all parts which have been
removed from the database.
The sample super transaction shown in Figure 2-6 would appear in the
>SWITCH listing as:
**BEGIN
**ADD
01BEGIN
01ADD
01DEL
01END
**DEL
**UPDATE
**END
Incomplete super transactions are reported in the same way. However, the
last **END record, and possibly other individual parts of the whole
transaction, will be missing.
Figure 2-7 shows the report generated showing completed super
transactions. Figure 2-8 shows the report generated showing incomplete
super transactions.
_____________________________________________________________________________
| |
| ===================================================================== |
| |
| List of successfully completed Silhouette Data Base Transactions |
| |
| ---User--- ---Program--- ---Data Base--- -Log#- -Ldev- |
| |
| MGR.ACT,ACCTS DRIVER1.ACCTS.ACT DBTST1.ACCTS.ACT 3373 3 |
| |
| **BEGIN-- **i00000000P** |
| **PUT---- MODE: 1 M-PRODUCT(Master M) i110Product i110 M1 .. |
| **PUT---- MODE: 1 M-PRODUCT(Master M) i111Product i111 M1 .. |
| 01begin-- **i00000000P** |
| 01PUT---- MODE: 1 M-PRODUCT(Master M) i110Product i110 M1 .. |
| 01PUT---- MODE: 1 M-PRODUCT(Master M) i111Product i111 M1 .. |
| 01end---- |
| 02begin-- **i00000000P** |
| 02PUT---- MODE: 1 M-PRODUCT(Master M) i110Product i110 M1 .. |
| 02PUT---- MODE: 1 M-PRODUCT(Master M) i111Product i111 M1 .. |
| 02end---- |
| **END---- |
| ======================================================================|
_____________________________________________________________________________
Figure 2-7. Report of Completed Super Transactions
_____________________________________________________________________________
| |
| ================================================================ |
| |
| List of * incomplete * ACCTS Data Base transactions |
| |
| ---User--- ---Program--- ---Data Base--- -Log#- -Ldev- |
| MGR.ACT,ACCTS DRIVER1.ACCTS.ACT |
| DBTST1.ACCTS.ACT 3373 3 |
| |
| **BEGIN-- **k0000000U1** |
| **BEGIN-- **k0000000U1** |
| 01begin-- **k0000000U1** |
| 02begin-- **k0000000U1** |
| **UPDATE- MODE: 1 M-PRODUCT(Master M) |
| 01update- MODE: 1 M-PRODUCT(Master M) |
| 01end---- |
| 02update- MODE: 1 M-PRODUCT(Master M) |
| 02end---- |
| |
| ======================================================================|
_____________________________________________________________________________
Figure 2-8. Report of Incomplete Super Transactions