请问关于数据操作回滚的有关问题

CREATE TABLE tb1 (id1 INT,id2 DECIMAL(4, 1))INSERT INTO tb1SELECT 1, 4.3UNION ALLSELECT 2, 234.2 现在把字段id2的数据类型改为decimal(4,2),数据库生成脚本如下：BEGIN TRANSACTIONSET QUOTED_IDENTIFIER ONSET ARITHABORT ONSET NUMERIC_ROUNDABORT OFFSET CONCAT_NULL_YIELDS_NULL ONSET ANSI_NULLS ONSET ANSI_PADDING ONSET ANSI_WARNINGS ONCOMMITBEGIN TRANSACTIONGOCREATE TABLE dbo.Tmp_tb1    (    id1 int NULL,    id2 decimal(4, 2) NULL     )  ON [PRIMARY]GOALTER TABLE dbo.Tmp_tb1 SET (LOCK_ESCALATION = TABLE)GOIF EXISTS(SELECT * FROM dbo.tb1)     EXEC('INSERT INTO dbo.Tmp_tb1 (id1, id2)        SELECT id1, id2 FROM dbo.tb1 WITH (HOLDLOCK TABLOCKX)')GODROP TABLE dbo.tb1GOEXECUTE sp_rename N'dbo.Tmp_tb1', N'tb1', 'OBJECT' GOCOMMIT如果这样执行操作，数据将会丢失，因为有数据溢出。问题：语句中的回滚操作怎么不生效呢？还是说回滚对这类操作无效呢？求教执行这类操作时如果进行数据回滚

CREATE TABLE tb1 (id1 INT,id2 DECIMAL(4, 1))INSERT INTO tb1SELECT 1, 4.3UNION ALLSELECT 2, 234.2 begin try begin tran   alter table tb1 alter column id2 DECIMAL(4, 2) commit tranend trybegin catch  rollback tran  select error_number() as error_number ,         error_message() as error_message,         error_state() as error_state,         error_severity() as error_severityend catch  error_number error_message                                                         error_state error_severity------------ --------------------------------- ----------- --------------8115         Arithmetic overflow error converting numeric to data type numeric.         8           16(1 row(s) affected)