public void setPerformCheckOnly(Boolean performCheckOnly) {
        this.performCheckOnly = performCheckOnly;
    }
<p>
This flag, when set to True, indicates that an Upgrade Eligibility Check needs to be performed. This will not
actually perform the Upgrade.
</p>

@param performCheckOnly
       This flag, when set to True, indicates that an Upgrade Eligibility Check needs to be performed. This will
       not actually perform the Upgrade.
aws-java-sdk-elasticsearch/src/main/java/com/amazonaws/services/elasticsearch/model/UpgradeElasticsearchDomainRequest.java