Caché ObjectScript Reference - InterSystems Documentation

You can issue a TROLLBACK 1 command to roll back the current level of nested transaction.You can issue a TROLLBACK to roll back the whole transaction, no matter how manylevels of TSTART were issued.You can use the $ZUTIL(78,21) function to search the journal file for TSTART commands,and thus identify open transactions. A TSTART writes either a “BT” (Begin Transaction)journal file record if $TLEVEL was zero, or a “BTL” (Begin Transaction with Level) journalfile record if $TLEVEL was greater than 0.The maximum number of levels of nested transactions is 255. Attempting to exceed thisnesting levels limit results in a error.SQL and TransactionsCaché ObjectScript transaction processing, using TSTART and TCOMMIT, differs from,and is incompatible with, SQL transaction processing using the SQL statements STARTTRANSACTION and COMMIT. Caché ObjectScript transaction processing provides limitedsupport for nested transactions; SQL transaction processing does not support nested transactions.An application should use one type of transaction processing throughout, and not attemptto mix the two.ArgumentspcAn optional postconditional expression. Caché executes the TSTART command if the postconditionalexpression is true and does not execute the TSTART command if the postconditionalexpression is false. For further details, refer to Command Postconditional Expressionsin Using Caché ObjectScript.ExamplesTSTARTThe following example shows nested pairs of TSTART/TCOMMIT amd the effects ofTROLLBACK on nested transactions. Each TSTART increments $TLEVEL and sets a global.Issuing a TCOMMIT on the inner nested transaction decrements $TLEVEL, but the commitmentof changes made in a nested transaction is deferred. In this case, the subsequentTROLLBACK on the outer transaction rolls back all changes made, including those in theinner “committed” nested transaction.Caché ObjectScript Reference 143