12.2.1. Batch inserts

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When you make new objects persistent, employ methods `flush()` and `clear()` to the session regularly, to control the size of the first-level cache.

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<div id="batch-session-batch-insert-example" class="exampleblock">
<div class="title">Example 300. Flushing and clearing the `Session`</div>
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<pre class="prettyprint highlight">`EntityManager entityManager = null;
EntityTransaction txn = null;
try {
    entityManager = entityManagerFactory().createEntityManager();

    txn = entityManager.getTransaction();
    txn.begin();

    int batchSize = 25;

    for ( int i = 0; i &lt; entityCount; ++i ) {
        Person Person = new Person( String.format( "Person %d", i ) );
        entityManager.persist( Person );

        if ( i &gt; 0 &amp;&amp; i % batchSize == 0 ) {
            //flush a batch of inserts and release memory
            entityManager.flush();
            entityManager.clear();
        }
    }

    txn.commit();
} catch (RuntimeException e) {
    if ( txn != null &amp;&amp; txn.isActive()) txn.rollback();
        throw e;
} finally {
    if (entityManager != null) {
        entityManager.close();
    }
}`</pre>
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