Fun & learning with Electrum EPS, Electrum wallet & Bitcoin Core QT in Win 11

[nc50lc]

I discovered EPS loads with my block read Bitcoin Core errors. The error is putting txindex=1 in bitcoin.conf it is not connected with EPS. Why did my Bitcoin Core have failed to read block error?

Have you experienced any power interruption before that error showed?
Or at least forced the machine to shutdown while Core is running?

Because that may be caused by a corrupted data in your bitcoin datadir.

You'll need to check the "debug.log" file in your bitcoin datadir to see the actual issue whether it can be solved by --reindex, --reindex-chainstate or not.
Look for something like "block checksum mismatch" within the last few lines and check if the corrupted file is in "blocks/index" directory, "chainstate" directory or the block itself.
The first two require you to run the matching command line arg above, the latter is a bad issue where you have to resyc your node.

[arabspaceship123]

Have you experienced any power interruption before that error showed?
Or at least forced the machine to shutdown while Core is running?

Because that may be caused by a corrupted data in your bitcoin datadir.

No power interruptions.

I forced Bitcoin Core 30 to shutdown once from task manager after upgrade because it takes time to convert legacy wallets to descriptor so I installed Core 29 like before the upgrade.

You'll need to check the "debug.log" file in your bitcoin datadir to see the actual issue whether it can be solved by --reindex, --reindex-chainstate or not.
Look for something like "block checksum mismatch" within the last few lines and check if the corrupted file is in "blocks/index" directory, "chainstate" directory or the block itself.
The first two require you to run the matching command line arg above, the latter is a bad issue where you have to resyc your node.

My debug log has some data.

WARNING: option -rpcallowip was specified without -rpcbind; this doesn't usually make sense
[error] ReadBlock: Deserialize or I/O error - ReadCompactSize(): size too large: iostream error at FlatFilePos(nFile=21, nPos=31361069)
[error] A fatal internal error occurred, see debug.log for details: Sync: Failed to read block 00000000000004e2fa8343d0601a27e43180359909b6d876557d7ce30aad9cec from disk

[nc50lc]

[error] ReadBlock: Deserialize or I/O error - ReadCompactSize(): size too large: iostream error at FlatFilePos(nFile=21, nPos=31361069)

This is bad, unlike chainstate or block index errors that I've mentioned that can be solved by --reindex
This particular error means that you "blk00021.dat" file has corrupted data. (an actual block file in your disk)

Force-closing Core usually doesn't cause this since that early block shouldn't be actively written to your disk.
I'd look at the disk's health, power and connectors in this case.

[arabspaceship123]

[error] ReadBlock: Deserialize or I/O error - ReadCompactSize(): size too large: iostream error at FlatFilePos(nFile=21, nPos=31361069)

This is bad, unlike chainstate or block index errors that I've mentioned that can be solved by --reindex
This particular error means that you "blk00021.dat" file has corrupted data. (an actual block file in your disk)

Force-closing Core usually doesn't cause this since that early block shouldn't be actively written to your disk.
I'd look at the disk's health, power and connectors in this case.

Disk is checked it is functional without errors. It has excellent health. Am I going to have failure in Bitcoin Core and EPS without putting txindex=1 in my bitcoin.conf? It should work for my wallet because I will not make blockchain analysis to look at data for other wallets.

[nc50lc]

Am I going to have failure in Bitcoin Core and EPS without putting txindex=1 in my bitcoin.conf?

No you're not since it's not required by EPS. (at least due to that specific setting)

But this is baffling because Bitcoin Core wont start with a block storage error while EPS still works.
Perhaps that's the reason why EPS fails with txindex since it has to scan the blocks to build the transaction index
While still somehow works without it.

[arabspaceship123]

Am I going to have failure in Bitcoin Core and EPS without putting txindex=1 in my bitcoin.conf?

No you're not since it's not required by EPS. (at least due to that specific setting)

But this is baffling because Bitcoin Core wont start with a block storage error while EPS still works.
Perhaps that's the reason why EPS fails with txindex since it has to scan the blocks to build the transaction index
While still somehow works without it.

I can use my Core arrangement if txindex=1 in bitcoin.conf is not affecting EPS. Bitcoin Core fails loading with the block error, it shuts down if clicking OK. If Bitcoin Core is not shutdown my EPS loads the watch only wallets. I was confused why Bitcoin Core does not start with the block storage error but EPS worked so I will test transactions.

[nc50lc]

I was confused why Bitcoin Core does not start with the block storage error but EPS worked so I will test transactions.

This is why I mentioned it's baffling, because EPS relies on RPC to communicate with the node which requires the node to be functioning.
I guess RPC still works since it can find Core and if EPS can still issue commands that doesn't require the blockchain like sendrawtransaction, your test transaction might work.

But I bet it would cause an error once it needs to rescan the blockchain.
e.g.: restoring an old wallet that requires to scan the affected block.

[arabspaceship123]

This is why I mentioned it's baffling, because EPS relies on RPC to communicate with the node which requires the node to be functioning.
I guess RPC still works since it can find Core and if EPS can still issue commands that doesn't require the blockchain like sendrawtransaction, your test transaction might work.

But I bet it would cause an error once it needs to rescan the blockchain.
e.g.: restoring an old wallet that requires to scan the affected block.

I was a new Bitcoin user I used rescan on another drive. Something was wrong in the Bitcoin Core download. It scanned for hours so I did not complete the scan I stopped. I do not want to run another scan because I am expecting it will fail. I will use my EPS and Core without putting txindex=1 in my bitcoin.conf because it works. Thanks for your help.