<h1 id="transaction">Transaction<a aria-hidden="true" class="anchor-heading icon-link" href="#transaction"></a></h1>
<h1 id="transaction-1">Transaction<a aria-hidden="true" class="anchor-heading icon-link" href="#transaction-1"></a></h1>
<p>Transaction is the <strong>execution of a sequence of one or more operations</strong> on a shared database to perform some higher level function. They are the basic unit of change in DBMS! It is a sequence of read and write operations. </p>
<p>The outcome of a transaction is either COMMIT or ABORT. If commit, all the transaction's modifications are saved to the database. If abort,  all the changes are undone so that this transaction is never happened. </p>
<p>一种操作要么全部步骤成功，要不都失败.其中就有commit point的概念，在这之前是可以undo操作的，之后不行</p>