On 10 Jun 2026 the 23,500 call of the 30 Jun Nifty series had 44,81,555 units of open interest, which is 68,947 lots of 65 units. Every one of those units had a buyer and a seller. The option chain says how many exist. It does not say who holds which side. A gamma exposure chart needs exactly that, because the people who hedge change their hedge as the index moves, and the sign of the hedge depends on the side they hold. This lesson asks who is on the other side in India, using the one public file that comes close: NSE's participant wise open interest. It has four groups, in contracts, for all index options together, at the close. I read it as a ledger first. What it says about the sign is less than a reel makes of it.
3By the end you can
- Say what the chain and the participant file each show about who holds the other side.
- Count the sessions a group was net short, and read why client is not the same as retail.
- Turn a group into a dealing side net long share, and say why that share is an assumption.
The idea, plainly
What the chain says, and what it leaves out
The option chain gives open interest in units for each strike and expiry. Calls and puts are counted separately, and for each one the long side equals the short side. The chain stops there. It has no holder, no category and no side. Module F18 reads the chain, and module I07 reads the participant file. This lesson joins them.
What the participant file adds
NSE publishes one file after each close, with open contracts for four groups: Client, DII, FII and Pro. Three limits matter here. The unit is contracts, so divide the chain's units by the lot. The file covers all index contracts together, so it cannot give a number for one strike or one expiry. And a group is a category of account, not a type of trader. Pro is the member firms' own accounts. Dealing desks can sit there, and the file does not flag market makers.
Read one more paragraph, 52 words
The file balances. Across the four groups the longs equal the shorts, so the net positions add up to zero, to within a couple of contracts on every session in the window. That is a ledger. It tells you the other side exists. It does not tell you whose view it was.
Why the sign matters
A dealer who is long gamma gains delta as the index rises and loses it as the index falls, so staying hedged means selling into rallies and buying dips. That steadies the index a little. A dealer who is short gamma does the reverse and chases the move. The size of the hedge follows the gamma of the book. The direction of the hedge follows the side the dealer holds. So every story about gamma exposure turns on one thing: is the hedger long or short the options?
Reading the sessions one by one
The copy used here starts on 1 Jul 2025, and up to 10 Jun 2026 it holds 233 sessions. For each group and for calls and puts separately, count the sessions on which the group's long contracts were fewer than its short contracts.
The client group was net short puts on every session, and FII was net short calls on most
Read one more paragraph, 105 words
Four patterns stand out. The client group was net short puts on every one of the sessions, and net long calls on most of them. FII was net long puts on every session and net short calls on most. That fits a holder who buys protection and sells calls against shares, though the file cannot prove it. Pro swapped sides on calls many times. DII is almost absent, because its net position is tiny. So the group that was net short puts all the time is the client group, which is not what a reel about retail traders buying options would lead you to expect.
Client is not retail
SEBI's Aug 2026 study of trading behaviour, FY25 to FY26, looked at a random sample of individual traders, which SEBI calls indicative. It found that 97% of them were mainly options buyers. Both facts can be true. The client group holds more than individuals. It takes in every account that is not a member, a DII or an FII, so it can hold firms that trade through client codes, corporates and wealthy accounts that write options. The file cannot split the group. So it cannot say whether the net short puts belong to the people SEBI counts as individuals. For the same reason the file cannot name a market maker.
What the file cannot do
- It has no strike and no expiry, so it cannot say who holds the weekly and who holds the monthly.
- It cannot split hedges from views. A foreign fund that sells calls against its shares and a desk that sells calls for a view look the same.
- It lists futures and options in separate columns, so a short call hedged with a long future shows as two positions in two places.
- It is a snapshot at the close. Through the day the sides change many times.
From a group to a sign
For gamma exposure the question is narrow: on which side is the group that hedges? You have to pick a group and trust the pick. The file then gives a number, the net position of that group as a share of all open interest in the product.
Two terms to hold on to from 15.8
The maths: dealing side net long share
For calls and for puts separately, take the long contracts less the short contracts of the groups you call the dealing side, divided by the total long contracts of all four groups. The result lies between minus one and one.
Share = (long − short
of dealing groups)
/ total long of all groups
Gamma exposure then uses this share as a signed weight on every call line, and a second one on every put line. A share of minus one says the dealing side is short every call. The three conventions are special cases: A uses plus one for calls and minus one for puts, B uses minus one for both, and C uses the shares from the file. Module A19 puts them to work.
The file turns open interest into a sign only after an assumption
Worked example: three choices, one day, 10 Jun 2026
Take the 23,500 strike on 10 Jun 2026. The call there held 44,81,555 units, which is 68,947 lots, and the put held 38,83,945 units. The file for that day has the call and put positions of all four groups, for every index at once, so it cannot say which of those lots belong to which group. It can give the dealing side's share of all open interest, under each choice of who that side is.
The sign changes with the group you pick, and with calls against puts
Reading the three shares
The shares are small fractions of open interest, nowhere near plus or minus one. Take Pro as the dealing side and both shares are small, so the group is nearly flat in aggregate and says little about the sign. Take FII and the shares are of opposite sign for calls and puts: short calls and long puts. Take both and the put share is larger still. None of the three is the plus one or minus one a simple convention assumes. Every number is an aggregate of all index contracts, so it need not describe the Nifty 30 Jun series.
Three conventions, one day
The three readings of the same day, in words:
- Convention A. The dealing side is the dealers, by the habit of US data. Sign: long calls, short puts.
- Convention B. The dealing side is the writers, since customers mostly buy. Sign: short both.
- Convention C. The dealing side is the group you choose in the participant file. Sign: that group's net share of open interest.
Read one more paragraph, 82 words
The file backs none of these as the truth. Under A, the pattern is that of the client group in the file: long calls and short puts. Under B, the pattern is nobody's in particular. Under C the answer changes with the group, as the chart shows. The next module, A19, shows what each choice does to a gamma exposure figure. The question pages is Nifty GEX reliable and who are the market makers and option sellers give the short version.
Where the dealing desks sit
One more piece of context. SEBI's Sep 2024 study of FY22 to FY24 found that most of the FY24 gross trading profit of proprietary traders and FPIs came from algorithmic trading. A dealing desk can sit in either group. The file shows neither as a steady net seller of both calls and puts.
Where this section sits in module 15.8
The GEX lab below carries the same participant data. Switch to convention C, pick the dealing group, and watch the total move.
The common mistake
The claim: Retail buys all the options, so the dealers are short everything and gamma exposure is always negative.
The file does not support the first part. On every one of the 233 sessions the client group was net short puts, and the group is wider than individuals. It does not support the second part either. Taking FII or Pro as the dealing side gives shares with signs that differ for calls and puts and that change from session to session. Convention B, short everything, is one assumption among several. So is A. A gamma exposure figure is a model of what hedging would follow if the assumption were true, and the file cannot say which assumption is. Before using a sign, ask which group you mean and why.
Key takeaways
- The chain has open interest in units and names no holder or side.
- The participant file has four groups in contracts, for all index options together.
- The client group was net short puts on every session.
- Client is not retail: it holds every account outside the other three.
- A chosen group's net share is small, and its sign depends on the pick.
- A gamma sign is an assumption, and the file cannot say which is right.
Before you trade. Derivatives trading carries a high risk of loss. SEBI's study "Profitability of Individual Traders in the Equity Derivatives Segment (FY25 to FY26)" (August 2026) found that 87.7% of individual traders in equity F&O made net losses in FY26, with aggregate net losses of Rs 91,685 crore. Read the SEBI study