| Format |
| | Begin_transaction [/Qualifiers... ] |
| | the BEGIN_TRANSACTION statement enables you to mark the beginning of a transaction. A transaction consists of one or more database updates which, because of their nature, must be treated as one autonomous unit. These updates may occur across multiple files. For example, a debit and credit must be treated as an autonomous unit in order to maintain accounting integrity. |
| | You can use BEGIN_TRANSACTION in conjunction with END_TRANSACTION and other available transaction statements to ensure that no part of a transaction is carried out if the entire transaction cannot be carried out. In the case of the debit/credit example, you can ensure that a debit never takes place without its associated credit. Either the entire transaction completes, or no portion of the transaction takes place at all. |
| | A BEGIN_TRANSACTION statement may not be executed while another transaction is current (i.e. no nesting is allowed). Additionally, while a transaction is current, databases cannot be closed. Either case results in the generation of an error if attempted. |
| | Any record locks that are active when a BEGIN_TRANSACTION statement is executed remain active, in spite of any attempted UNLOCKS, until an END_TRANSACTION is executed. Once the END_TRANSACTION is executed, record lock status is as it normally would have been if a transaction had never been defined. |
| | For RMS files, Recovery Unit (RU) journaling implements transactions. You may begin a transaction regardless of whether or not RU journaling has been enabled for data files. However, data integrity is only ensured for data files marked for RU journaling. When an IDML program terminates for any reason (e.g. system crash, normal program exit, etc.), and a transaction is current, all data files marked for RU journaling are restored to their state prior to the occurrence of the transaction. |
| Qualifiers |
 | /Fail=LABEL | Label to which to branch if the statement fails.
If LABEL is %EXIT, exit the routine or loop.
If in a loop, and LABEL is %CONTINUE, continue the loop. If not in a loop, and LABEL is %CONTINUE, an error message displays. | | |
| | /Succeed=LABEL | Label to which to branch if the statement succeeds.
If LABEL is %EXIT, exit the routine or loop. If in a loop, and LABEL is %CONTINUE, continue the loop. If not in a loop, and LABEL is
%CONTINUE, an error message displays. | | |
| | /Nofail | Do not signal an error. Instead, set the
internal variable %FAIL. | | |
| Example |
| | !****************************** |
| | ! Form TRANSFER |
| | !****************************** |
| | |
| | Form TRANSFER & |
| | /Pos=2, 10 /Size=3,60 & |
| | Border="Transfer funds" & |
| | /Flow & |
| | /Text=1, 15, "Checkings balance:" & |
| | /Text=2, 16, "Savings balance:" & |
| | |
| | Output CHECKING_BAL(BALANCE) /Pos=1,33 |
| | Output SAVINGS_BAL(BALANCE) /Pos=2,33 |
| | |
| | If xfer_direction = "Checking_to_savings" |
| | prompt = "Checking to savings:" |
| | Else |
| | prompt = "Savings to checking:" |
| | End_if |
| | |
| | Loop |
| | ! Get balance records for update |
| | Get "1" in CHECKING_BAL /Lock=Write |
| | Get "1" in SAVINGS_BAL /Lock=Write |
| | Show/Outputs |
| | |
| | ! Get amount to be transferred |
| | Input amount /Pos=3,33 & |
| | /Exit=END & |
| | /Prompt=prompt & |
| | /Using=CHECKING_BAL(BALANCE) & |
| | /Verify=MUST_BE_POSITIVE |
| | |
| | ! Begin a transaction |
| | Begin_transaction |
| | ! Update the balances |
| | If xfer_direction = "Checking_to_savings2 |
| | If CHECKING_BAL(BALANCE) amount then |
| | Error "Checking account went negative." |
| | CHECKING_BAL(BALANCE) = CHECKING_BAL(BALANCE) - amount |
| | SAVINGS_BAL(BALANCE) = SAVINGS_BAL(BALANCE)+ amount |
| | Else |
| | If SAVINGS_BAL(BALANCE) = amount |
| | SAVINGS_BAL(BALANCE) = SAVINGS_BAL(BALANCE) - amount |
| | CHECKING_BAL(BALANCE) = CHECKING_BAL(BALANCE) + amount |
| | Else |
| | ! Insufficient funds in savings, abort the transaction and re-prompt |
| | Error "Insufficient funds in savings account." |
| | Abort_transaction |
| | Continue |
| | End_if |
| | End_if |
| | Show /Outputs |
| | ! Prompt to accept the transfer of funds. If the transfer is accepted, |
| | ! end the transaction with the already updated balances. If the transfer |
| | ! is rejected, rollback the transaction (restoring the balances to their |
| | ! states prior to the beginning of the transaction. |
| | Menu ACCEPT |
| | If %ITEM = "YES" then |
| | Message "Transaction accepted." |
| | End_transaction |
| | Else |
| | Message "Transaction not accepted. Accounts reset to previous state." |
| | Abort_transaction ! (Rollback) |
| | End_if |
| | End_loop |
| | END: |
| | Endform |