public Boolean isPerformCheckOnly() {
        return this.performCheckOnly;
    }
<p>
When true, indicates that an upgrade eligibility check needs to be performed. Does not actually perform the
upgrade.
</p>

@return When true, indicates that an upgrade eligibility check needs to be performed. Does not actually perform
        the upgrade.
aws-java-sdk-opensearch/src/main/java/com/amazonaws/services/opensearch/model/UpgradeDomainRequest.java