“Transaction Summary” reports committed transactions. “Committed Xacts” reports the number of transactions committed during the sample interval.
The count of transactions includes transactions that meet explicit, implicit, and ANSI definitions for “committed”, as described here:
An implicit transaction executes data modification commands such as insert, update, or delete. If you do not specify a begin transaction statement, Adaptive Server interprets every operation as a separate transaction; an explicit commit transaction statement is not required. For example, the following is counted as three transactions.
1> insert … 2> go 1> insert … 2> go 1> insert … 2> go
An explicit transaction encloses data modification commands within begin transaction and commit transaction statements and counts the number of transactions by the number of commit statements. For example the following set of statements is counted as one transaction:
1> begin transaction 2> insert … 3> insert … 4> insert … 5> commit transaction 6> go
In the ANSI transaction model, any select or data modification command starts a transaction, but a commit transaction statement must complete the transaction. sp_sysmon counts the number of transactions by the number of commit transaction statements. For example, the following set of statements is counted as one transaction:
1> insert … 2> insert … 3> insert … 4> commit transaction 5> go
If there were transactions that started before the sample interval began and completed during the interval, the value reports a larger number of transactions than the number that started and completed during the sample interval. If transactions do not complete during the interval, “Total # of Xacts” does not include them. In Figure 39-1, both T1 and T2 are counted, but T3 is not.
Figure 39-1: How transactions are counted