Ogg-01184 Expected 4 Bytes But Got 0 Bytes In Trail

The error OGG-01184: Expected 4 bytes but got 0 bytes in trail is a critical Oracle GoldenGate message indicating that a process (usually a Pump or Replicat) failed to read a mandatory 4-byte record trailer token from a trail file. This typically occurs when a record is incomplete or the file has been truncated prematurely. Understanding the Root Causes

The "expected 4 bytes but got 0" condition signifies that the GoldenGate process reached a Relative Byte Address (RBA) where it expected to find metadata, but instead encountered the end of the file.

Trail File Corruption: This is the most common cause. A trail file may be corrupted due to underlying disk issues, filesystem failures, or an abrupt system shutdown that prevented the Extract from properly closing the file.

Abnormal Process Termination: If the source Extract process crashes while writing, it may leave a "short" record at the end of the trail file that lacks the necessary closing tokens.

Checkpoint Mismatch: Sometimes, the input checkpoint position for a Pump or Replicat is greater than the actual physical size of the trail file, leading the process to seek data that does not exist.

Network Issues: In remote trail scenarios, network interruptions during a transfer can result in a partial file being written to the target system. Step-by-Step Troubleshooting and Resolution 1. Identify the Corrupted Trail File and RBA

Check the GoldenGate Error Log (usually ggserr.log) to find the specific sequence number and RBA where the error occurred.

Example Error: ERROR OGG-01184 Expected 4 bytes, but got 0 bytes, in trail ./dirdat/no000007, seqno 7, reading record trailer token at RBA 246849346.. 2. Verify File Integrity

Compare the RBA mentioned in the error with the actual size of the trail file on the disk. If the RBA is larger than the file size, the file is definitely truncated. 3. Resolution Strategies

Option A: Automated Remote Trail Recovery (OGG 12.2+)If you are using Oracle GoldenGate 12.2 or higher, you can often recover remote trails automatically: Stop the Pump process on the source. Delete the corrupted trail file from the target.

Restart the Pump; it will automatically rebuild and re-send the missing trail files from the source. ogg-01184 expected 4 bytes but got 0 bytes in trail

Option B: Repositioning the ProcessIf the corruption is at the very end of a trail file and the next trail file exists, you can skip the corrupted record:

Use ALTER REPLICAT , EXTTRAILSOURCE , RBA to move past the error. Note that this may result in data loss for that specific record.

Option C: Re-extracting DataIf the local trail on the source is corrupted, you must re-position the Extract process to a point in the database logs (SCN or timestamp) prior to the corruption and regenerate the trails. Prevention Best Practices

Monitor Disk Space: Ensure the dirdat directory has enough space to prevent partial writes.

Use Proper Shutdowns: Always use the STOP command in GGSCI rather than killing OS processes.

Filesystem Stability: Host trail files on stable, high-performance filesystems to reduce the risk of I/O related corruption. OGG-01184 - Oracle GoldenGate Error Messages

Expected 3,number,0 bytes, but got 4,number,0 bytes, in trail 0, seqno 1,number,0, reading record trailer token at RBA {2, Oracle Help Center Extract & Pump Abends - Oracle Communities

The error OGG-01184 indicates that an Oracle GoldenGate process (Extract, Pump, or Replicat) encountered a corrupted trail record. Specifically, the process expected to find a 4-byte trailer token at a specific Relative Byte Address (RBA) but found 0 bytes instead, typically because the record length in the trail file does not match the actual data present. Error Breakdown Error Code: OGG-01184

Message: Expected 4 bytes, but got 0 bytes, in trail [path], seqno [number], reading record trailer token at RBA [number].

Primary Cause: Corruption in the trail file. This often happens if a process (like a Pump) tries to read beyond the actual end of a file, or if a network/disk failure caused an incomplete write. Troubleshooting & Resolution Steps Identify the Corruption Point The error OGG-01184: Expected 4 bytes but got

Note the Trail File Path, Sequence Number, and RBA provided in the error message.

Compare the reported RBA against the actual size of the file on the disk. If the RBA is greater than the file size, the process is attempting to read "ghost" data. Verify Process Checkpoints

Use the command INFO [process_name], SHOWCH in GGSCI to see the current read and write checkpoints.

Confirm if the trail file actually exists and isn't a directory mistakenly named after a checkpoint file. Perform a Trail Rollover (If on Source/Pump)

If the source Extract or Pump is the one failing, force it to start a new trail file to skip the corrupted segment:ALTER [process_name], ETROLLOVER.

After rolling over, you may need to reposition the downstream process to the new sequence number. Reposition the Process

If you can afford to skip the corrupted record, reposition the failing process to the next valid RBA or the next trail file sequence:ALTER [process_name], EXTSEQNO [next_seq], EXTRBA 0. Re-read or Regenerate (Last Resort)

If the trail file is severely corrupted and data integrity is critical, you may need to delete and re-add the process or re-extract the data from the source.

Check for disk space issues or network jitter, as these are common environmental causes for trail corruption. Reference Documentation

For further details, consult the Oracle GoldenGate Error Messages Guide or search My Oracle Support (MOS) for Doc ID 1138409.1, which specifically addresses RBA mismatches. OGG-01184 - Oracle GoldenGate Error Messages For Oracle-specific files or operations, Oracle Support can

Expected 3,number,0 bytes, but got 4,number,0 bytes, in trail 0, seqno 1,number,0, reading record trailer token at RBA {2, Oracle Help Center OGG-01184 - Oracle GoldenGate Error Messages

Expected 3,number,0 bytes, but got 4,number,0 bytes, in trail 0, seqno 1,number,0, reading record trailer token at RBA {2, Oracle Help Center Extract & Pump Abends — oracle-mosc

Here’s a structured incident and troubleshooting report for the Oracle GoldenGate error:

4. Consult Oracle Support

1. Understanding the Oracle GoldenGate Trail File Format

Before diving into the error, it’s essential to understand GoldenGate trail files. A trail file (e.g., dirdat/aa000001) is a binary file where GoldenGate writes captured data changes (INSERT, UPDATE, DELETE). The file is structured in records or chunks, each with a specific header and payload.

The 4 bytes referenced in the error message refer to the record length prefix. In OGG trail files, each logical record is preceded by a 4-byte integer that indicates the total length of the following data payload. This design allows GoldenGate processes to read the file sequentially, knowing exactly how many bytes to read for the next record.

When GoldenGate’s Replicat or a downstream process tries to read a trail file, it first reads these 4 bytes. If the file is corrupted, truncated, or ends prematurely, the process might read 0 bytes instead of a valid 4-byte length header, leading to the OGG-01184 error.

What is a GoldenGate Trail File?

Before fixing the error, you must understand what GoldenGate is trying to read. A trail file (e.g., dirdat/rt000001) is a binary sequence of records. Each record represents a database operation (INSERT, UPDATE, DELETE, DDL). The structure is:

| Field | Size | Description | |-------|------|-------------| | Record Length | 4 bytes | Indicates the total size of the following data | | Record Data | Variable | Actual change data in canonical format | | Checksum (optional) | 4 bytes | Integrity check |

The error ogg-01184 expected 4 bytes but got 0 bytes occurs when GoldenGate’s reader reaches a point in the trail file where it expects to read the Record Length header, but the file ends abruptly. The system reads 0 bytes instead of 4.