CHAIN/UPDATE/DELETE

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Here’s a clear explanation and working examples of the CHAIN, UPDATE, and DELETE operations in free-form RPGLE, including how to handle record locks and status codes safely.

🔁 1. CHAIN (Read a Record by Key)

The CHAIN operation retrieves a record from a keyed file using its key.

✅ Syntax:

Chain (CustomerID) Customers;

🔍 Example:

**FREE
Dcl-F Customers Usage(*Update) Keyed;

Dcl-S CustomerID Char(10) Inz('C123');

Chain (CustomerID) Customers;

If %Found(Customers);
   Dsply ('Customer: ' + %Trim(Name));
Else;
   Dsply ('Customer not found');
EndIf;

  • %Found() checks if a record was found.

  • %Error() + %Status can check for locks or other issues.

🔧 2. UPDATE (Write Back to File)

The UPDATE operation updates the record that was previously read via CHAIN, READ, etc.

✅ Example:

If %Found(Customers);
   Name = 'Updated Name';
   Update Customers;
EndIf;

🔍 With Lock Detection:

Update Customers;

If %Error and %Status = 1218;
   Dsply ('Record is locked, cannot update.');
EndIf;

🧹 3. DELETE (Remove a Record)

Deletes the current record (previously read with CHAIN or READ).

✅ Example:

Chain (CustomerID) Customers;

If %Found(Customers);
   Delete Customers;
EndIf;

🧾 Full Example: CHAIN → UPDATE → DELETE

**FREE
Ctl-Opt DftActGrp(*No) ActGrp(*Caller);

Dcl-F Customers Usage(*Update) Keyed;

Dcl-S CustomerID Char(10) Inz('C123');

Chain (CustomerID) Customers;

If %Error and %Status = 1218;
   Dsply 'Record is locked. Try later.';
ElseIf %Found(Customers);
   Dsply ('Customer: ' + %Trim(Name));

   // Update
   Name = 'New Name';
   Update Customers;

   // Delete
   Delete Customers;

   Dsply 'Customer updated and deleted.';
Else;
   Dsply 'Customer not found.';
EndIf;

*INLR = *On;
Return;

🧠 Tips:

Operation Purpose Needs *Update? Lock-safe?
CHAIN Read by key Only if updating Yes
UPDATE Save modified record ✅ Yes Check lock
DELETE Delete current record ✅ Yes Check lock

 

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