<?xml version="1.0"?>
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    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-08-01</periodOfReport>

    <issuer>
        <issuerCik>0001341439</issuerCik>
        <issuerName>ORACLE CORP</issuerName>
        <issuerTradingSymbol>ORCL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001205005</rptOwnerCik>
            <rptOwnerName>CATZ SAFRA</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O DELPHI ASSET MGMT CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>5525 KIETZKE LANE, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>RENO</rptOwnerCity>
            <rptOwnerState>NV</rptOwnerState>
            <rptOwnerZipCode>89511</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <officerTitle>Chief Executive Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

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                </transactionShares>
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                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
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                </directOrIndirectOwnership>
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                    <value>70312</value>
                </transactionShares>
                <transactionPricePerShare>
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                </transactionPricePerShare>
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                </sharesOwnedFollowingTransaction>
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                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness></transactionTimeliness>
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                </transactionShares>
                <transactionPricePerShare>
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                </transactionPricePerShare>
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                </transactionAcquiredDisposedCode>
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                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness></transactionTimeliness>
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                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
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    </nonDerivativeTable>

    <derivativeTable>
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            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
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                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
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                </transactionAcquiredDisposedCode>
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            <exerciseDate>
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            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>85937</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                </sharesOwnedFollowingTransaction>
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                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
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            </securityTitle>
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            <transactionDate>
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            </transactionDate>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
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            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
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                </transactionShares>
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                </transactionPricePerShare>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>85937</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                </sharesOwnedFollowingTransaction>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Performance Stock Unit</value>
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            <transactionDate>
                <value>2017-08-01</value>
            </transactionDate>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
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                </transactionShares>
                <transactionPricePerShare>
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                    <value>70312</value>
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        <derivativeTransaction>
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                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                <transactionShares>
                    <value>70312</value>
                    <footnoteId id="F3"/>
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                <transactionPricePerShare>
                    <value>0</value>
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                    <value>Common Stock</value>
                </underlyingSecurityTitle>
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                    <value>70312</value>
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                    <value>D</value>
                </directOrIndirectOwnership>
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        <derivativeTransaction>
            <securityTitle>
                <value>Performance Stock Unit</value>
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            <transactionDate>
                <value>2017-08-01</value>
            </transactionDate>
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                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>105468</value>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
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            <expirationDate>
                <footnoteId id="F4"/>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>105468</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>105468</value>
                </sharesOwnedFollowingTransaction>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Performance Stock Unit</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-08-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>105468</value>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F4"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>105468</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Shares withheld for payment of tax liability upon vesting of performance stock units.</footnote>
        <footnote id="F2">Represents amount of performance stock units earned from awards granted on July 24, 2014 and October 5, 2014 based on the achievement of performance targets for the fiscal year ended May 31, 2017, as determined by the Compensation Committee on August 1, 2017. The earned amount vested immediately. The number of earned performance stock units represents 50% of the target number of performance stock units eligible to be earned for the third performance period. The performance goals measured Oracle's performance against both a relative revenue growth metric (weighted 50%) and a relative operating cash flow metric (weighted 50%).</footnote>
        <footnote id="F3">Represents amount of performance stock units earned from an award granted on July 2, 2015 based on the achievement of performance targets for the fiscal year ended May 31, 2017, as determined by the Compensation Committee on August 1, 2017. The earned amount vested immediately. The number of earned performance stock units represents 50% of the target number of performance stock units eligible to be earned for the second performance period. The performance goals measured Oracle's performance against both a relative revenue growth metric (weighted 50%) and a relative operating cash flow metric (weighted 50%).</footnote>
        <footnote id="F4">Represents amount of performance stock units earned from an award granted on June 30, 2016 based on the achievement of performance targets for the fiscal year ended May 31, 2017, as determined by the Compensation Committee on August 1, 2017. The earned amount vested immediately. The number of earned performance stock units represents 75% of the target number of performance stock units eligible to be earned for the first performance period. The performance goals measured Oracle's performance against both a relative revenue growth metric (weighted 50%) and a relative operating cash flow metric (weighted 50%).</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/Lori A. Clancy by Lori A. Clancy, Attorney in Fact for Safra Catz (POA Filed 03-29-16)</signatureName>
        <signatureDate>2017-08-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
