MEMX options directory outlines instrument data and update process

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MEMX options directory guide

Highlights

MEMX publishes the Instrument Directory file for options around 6 a.m. Eastern, with possible updates during the day to reflect corrections or changes.
Fields like optionsSecurityId, underlier, maturityDate, strikePrice, and optionsProduct offer granular identification and differentiation of equity options products on MEMX.
MEMX warns users about potential inaccuracies in the directory, urging brokers and trading firms to check for intraday changes and maintain internal validation processes.

Directory fields and update schedule

As reported by MEMX, the Instrument Directory file is published for customer use at their own discretion and is typically posted at about 6 a.m. Eastern Time. The exchange says the file can be updated after its initial publication to reflect corrections or intraday changes, and end users remain responsible for identifying both daily and intraday deltas.

The notice explains that the optionsSecurityId field is a unique eight-character base 62 value used in MEMOIR feeds when market data updates are reported for a product, and it is also used to identify an instrument on the MEMO SBE protocol. Fields including underlier, optionRoot, maturityDate, strikePutCall, strikePrice and osiSymbol can be used to identify an option contract.

MEMX also says the optionsProduct field distinguishes between index and equity products, although only equity options are currently available for trading on the venue. The closingOnly field indicates whether the exchange accepts opening orders in a series, while closingTime shows when a series stops trading, isTestSymbol indicates whether a series is cleared at the OCC, and memoirStripe identifies the MEMOIR multicast channel used to send market data for the instrument.

Operational implications for options users

A symbol-to-securityId mapping does not change once assigned, according to the notice, while additional symbols are mapped to new securityIds. That structure gives firms a stable identifier for existing instruments even as the exchange adds new listings.

For brokers, vendors and trading firms connected to MEMX Options, the guidance underscores the need to monitor the directory throughout the session rather than rely only on the morning file. The exchange's warning that it does not guarantee absolute accuracy in the directory means market participants need internal checks when handling option reference data and intraday changes.

Our earlier coverage of the FCA’s new UK aggregate short-selling disclosures highlighted apparent errors and inconsistencies in the first published datasets, including figures that disappeared or changed between daily reports without clear revision notes. We noted that these issues raised concerns for traders and regulators who depend on timely, accurate records, especially under the new regime that lowers the disclosure threshold and relies on firms’ reporting quality.

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