Transaction PDAs reference accounts where the transaction data is stored. Transaction accounts contain various low level information like the number of approvals, rejections, the transaction authority, etc.
Transaction PDAs are derived from the multisig PDA and the transaction index. The transaction index is an easy way to derive a list of transactions related to the multisig. When a new transaction account is created, the multisig will bump up the transaction index by one. The current transaction index can be found in the multisig account. A newly created multisig will have a starting transaction index of 0.
To find a transaction PDA using the Anchor Web3 library:
Note that in the example,
transactionIndexis supplied as a BN. You are free to supply the transaction index anyway you prefer, as long as the value provided to
findProgramAddressis a little endian 4 byte buffer.
The format for deriving transaction PDAs is as follows:
["squad", multisig, transactionIndex, "transaction"]