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MQL5 runtime error reference

MQL5 Error 4806: Requested indicator data not found

MQL5 error 4806 officially means "Requested indicator data not found." CopyBuffer returned -1 or fewer values than requested because the handle, buffer index, calculation state, history, or requested range was not ready or valid. Validate the handle and buffer number, wait until BarsCalculated reports enough values, then accept only the number CopyBuffer actually returns. Do not read destination elements that were not copied. Capture GetLastError immediately around the failing call so an older error is not mistaken for the current failure.

Open MQL5 Coding AgentReview the diagnostic example

Open the Coding Agent and choose MQL5 from the language menu.

Isolate runtime error 4806.mq5
bool ReadLatestValue(const int handle,const int buffer,double &value)
  {
   if(handle==INVALID_HANDLE || BarsCalculated(handle)<1) return false;

   double values[1];
   ResetLastError();
   int copied=CopyBuffer(handle,buffer,0,1,values);
   if(copied!=1)
     {
      PrintFormat("CopyBuffer copied=%d error=%d",copied,GetLastError());
      return false;
     }
   value=values[0];
   return true;
  }
  • Official meaning: Requested indicator data not found
  • Layer: terminal runtime
  • Read with: GetLastError
  • First step: isolate the failing call

Also searched as: mql5 copybuffer error 4806.

Where error 4806 comes from

CopyBuffer returned -1 or fewer values than requested because the handle, buffer index, calculation state, history, or requested range was not ready or valid. The numeric value is listed in the official runtime error table, which is separate from MetaEditor compilation errors and trade server return codes.

Reset the last-error state before the suspected call, save its direct return value, and read GetLastError immediately afterward. This produces a causal log instead of a stale code.

Checks that narrow the cause

Preserve the exact parameters and terminal context that produced the failure. Check one precondition at a time before adding retries.

  • Reject INVALID_HANDLE before CopyBuffer.
  • Match the buffer number to the indicator output contract.
  • Require BarsCalculated(handle) to cover the requested range.
  • Check copied against the requested count before indexing the destination array.

Apply the smallest repair

Validate the handle and buffer number, wait until BarsCalculated reports enough values, then accept only the number CopyBuffer actually returns. Do not read destination elements that were not copied.

After the repair, test both the expected path and a deliberately invalid input. The second test confirms that the diagnostic branch still exposes failures.

Use a focused diagnostic

The wrapper waits for at least one calculated value and reads the output only when CopyBuffer confirms one copy. Larger ranges need the same count discipline.

A clean compile or a cleared error code does not prove strategy logic, broker compatibility, backtest quality, or live-trading safety. Reproduce the result in the target MetaTrader 5 terminal and account environment.

Isolate runtime error 4806.mq5
bool ReadLatestValue(const int handle,const int buffer,double &value)
  {
   if(handle==INVALID_HANDLE || BarsCalculated(handle)<1) return false;

   double values[1];
   ResetLastError();
   int copied=CopyBuffer(handle,buffer,0,1,values);
   if(copied!=1)
     {
      PrintFormat("CopyBuffer copied=%d error=%d",copied,GetLastError());
      return false;
     }
   value=values[0];
   return true;
  }
Where Pineify fits

Repair editable MQL5 source with compiler feedback

Pineify can generate or revise MQL5 source and use MQL5 compilation diagnostics during the coding workflow. Keep the exact error, source location, program type, and intended behavior in the request so the change remains reviewable.

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Pineify does not run your broker terminal, Strategy Tester, market data, or live orders. Validate the final program in your own MetaTrader 5 environment.

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A practical verification workflow

  1. 1

    Reset the error state

    Call ResetLastError directly before the suspected function so the next code belongs to that operation.

  2. 2

    Record call and inputs

    Save the function return value, every input, and GetLastError. Confirm that the captured runtime code is 4806.

  3. 3

    Validate the preconditions

    Reject INVALID_HANDLE before CopyBuffer. Match the buffer number to the indicator output contract. Require BarsCalculated(handle) to cover the requested range. Check copied against the requested count before indexing the destination array.

  4. 4

    Retest in the target terminal

    Compile the changed source, repeat the failing operation, and test the surrounding EA or indicator behavior in MetaTrader 5.

Frequently asked questions

What does MQL5 error 4806 mean?

The official runtime error table defines 4806 as "Requested indicator data not found."

Is error 4806 a compiler error?

No in this context. It is a terminal runtime code. Compiler diagnostics and MqlTradeResult.retcode values use separate code tables.

Why should I call ResetLastError first?

The terminal stores the last runtime error. Resetting it before the suspected call makes the following GetLastError value easier to attribute to that call.

Last verified against the linked official references on . Compile and test the final source in the MetaTrader 5 build, broker, symbol, and account environment you plan to use.

Continue with reviewable MQL5 source

Provide the exact diagnostic and intended behavior, inspect the generated change, compile it, and verify it in your MT5 test environment.

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