ILog::AppendRecord method (txlogpub.h)

Article
10/13/2021

Write a new record to the end of the log.

Syntax

HRESULT AppendRecord(
  [in]      BLOB  *rgBlob,
  [in]      ULONG cBlob,
  [in]      BOOL  fForceNow,
  [in, out] LSN   *plsn
);

Parameters

[in] rgBlob

A pointer to an array of BLOBs of data to be written.

[in] cBlob

The size of the rgBlob array, in elements.

[in] fForceNow

Indicates whether to force the data to disk. If TRUE, the contents of the log up to this record must be forced to disk before the call returns. If FALSE, this record may be buffered in memory to be written after the call returns successfully.

[in, out] plsn

A pointer to the LSN of the newly appended record. If the LSN of the newly appended record is not needed, this parameter can be NULL.

Return value

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

Each log record written or read by ILog is an opaque BLOB of data. As a convenience to callers, AppendRecord allows multiple BLOBs to be concatenated into a single record; because many implementations of ILog will copy records to a buffer in memory, it may be inefficient for the caller to allocate memory for concatenating the parts of a record. However, once a record is appended to the log, ILog provides no method to extract individual BLOBs from the record. It is the responsibility of the caller to parse the data in records read from the log. See ILog::ReadRecord.

Notes to Callers

A failure return value indicates that any records appended to the log since the last time it was successfully forced are not guaranteed to be on disk. The ILog interface does not provide a method to determine which records have been successfully written to disk. If you need to know which records were successfully written to disk, you must force the log for each record.

Notes to Implementers

If fForceNow is TRUE, it is recommended that you flush file buffers (for example, using the FlushFileBuffers function) before returning from this method.

Requirements

Requirement	Value
Minimum supported client	Windows XP [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Target Platform	Windows
Header	txlogpub.h

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