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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<title>Reviewing Berkeley DB log files</title>
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<p>Library Version 12.1.6.1</p>
</div>
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">Reviewing Berkeley DB log files</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="debug_runtime.html">Prev</a> </td>
<th width="60%" align="center">Chapter 3. Debugging Applications </th>
<td width="20%" align="right"> <a accesskey="n" href="build_android_intro.html">Next</a></td>
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="debug_printlog"></a>Reviewing Berkeley DB log files</h2>
</div>
</div>
</div>
<div class="toc">
<dl>
<dt>
<span class="sect2">
<a href="debug_printlog.html#idp164880">Augmenting the Log for Debugging</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="debug_printlog.html#idp136104">Extracting Committed Transactions and Transaction Status</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="debug_printlog.html#idp166064">Extracting Transaction Histories</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="debug_printlog.html#idp171384">Extracting File Histories</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="debug_printlog.html#idp183288">Extracting Page Histories</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="debug_printlog.html#idp184088">Other log processing tools</a>
</span>
</dt>
</dl>
</div>
<p>
If you are running with transactions and logging, the
<a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility can be a useful debugging aid. The <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility
will display the contents of your log files in a human
readable (and machine-readable) format.
</p>
<p>
The <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility will attempt to display any and all log
files present in a designated db_home directory. For each log
record, the <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility will display a line of the form:
</p>
<pre class="programlisting">
[22][28]db_big: rec: 43 txnid 80000963 prevlsn [21][10483281]</pre>
<p>
The opening numbers in square brackets are the
<span class="emphasis"><em>log sequence number</em></span>
(<span class="emphasis"><em>LSN</em></span>) of the log record being
displayed. The first number indicates the log file in which
the record appears, and the second number indicates the offset
in that file of the record.
</p>
<p>
The first character string identifies the particular log
operation being reported. The log records corresponding to
particular operations are described following. The rest of the
line consists of name/value pairs.
</p>
<p>
The rec field indicates the record type (this is used to
dispatch records in the log to appropriate recovery
functions).
</p>
<p>
The txnid field identifies the transaction for which this
record was written. A txnid of 0 means that the record was
written outside the context of any transaction. You will see
these most frequently for checkpoints.
</p>
<p>
Finally, the prevlsn contains the LSN of the last record
for this transaction. By following prevlsn fields, you can
accumulate all the updates for a particular transaction.
During normal abort processing, this field is used to quickly
access all the records for a particular transaction.
</p>
<p>
After the initial line identifying the record type, each
field of the log record is displayed, one item per line. There
are several fields that appear in many different records and a
few fields that appear only in some records.
</p>
<p>
The following table presents each currently written log
record type with a brief description of the operation it
describes. Any of these record types may have the string
"_debug" appended if they were written because
<a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_TXN_NOT_DURABLE" class="olink">DB_TXN_NOT_DURABLE</a> was specified and the system was
configured with <a class="link" href="build_unix_conf.html#build_unix_conf.--enable-diagnostic">--enable-diagnostic</a>.
</p>
<div class="informaltable">
<table border="1" width="80%">
<colgroup>
<col />
<col />
</colgroup>
<thead>
<tr>
<th>Log Record Type</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td>bam_adj</td>
<td>Used when we insert/remove an index
into/from the page header of a Btree
page.</td>
</tr>
<tr>
<td>bam_cadjust</td>
<td>Keeps track of record counts in a Btree or
Recno database.</td>
</tr>
<tr>
<td>bam_cdel</td>
<td>Used to mark a record on a page as
deleted.</td>
</tr>
<tr>
<td>bam_curadj</td>
<td>Used to adjust a cursor location when a
nearby record changes in a Btree
database.</td>
</tr>
<tr>
<td>bam_merge</td>
<td>Used to merge two Btree database pages
during compaction.</td>
</tr>
<tr>
<td>bam_pgno</td>
<td>Used to replace a page number in a Btree
record.</td>
</tr>
<tr>
<td>bam_rcuradj</td>
<td>Used to adjust a cursor location when a
nearby record changes in a Recno
database.</td>
</tr>
<tr>
<td>bam_relink</td>
<td>Fix leaf page prev/next chain when a page
is removed.</td>
</tr>
<tr>
<td>bam_repl</td>
<td>Describes a replace operation on a
record.</td>
</tr>
<tr>
<td>bam_root</td>
<td>Describes an assignment of a root
page.</td>
</tr>
<tr>
<td>bam_rsplit</td>
<td>Describes a reverse page split.</td>
</tr>
<tr>
<td>bam_split</td>
<td>Describes a page split.</td>
</tr>
<tr>
<td>crdel_inmem_create</td>
<td>Record the creation of an in-memory named
database.</td>
</tr>
<tr>
<td>crdel_inmem_remove</td>
<td>Record the removal of an in-memory named
database.</td>
</tr>
<tr>
<td>crdel_inmem_rename</td>
<td>Record the rename of an in-memory named
database.</td>
</tr>
<tr>
<td>crdel_metasub</td>
<td>Describes the creation of a metadata page
for a subdatabase.</td>
</tr>
<tr>
<td>db_addrem</td>
<td>Add or remove an item from a page of
duplicates.</td>
</tr>
<tr>
<td>db_big</td>
<td>Add an item to an overflow page
(<span class="emphasis"><em>overflow pages</em></span>
contain items too large to place on the main
page)</td>
</tr>
<tr>
<td>db_cksum</td>
<td>Unable to checksum a page.</td>
</tr>
<tr>
<td>db_debug</td>
<td>Log debugging message.</td>
</tr>
<tr>
<td>db_noop</td>
<td>This marks an operation that did nothing
but update the LSN on a page.</td>
</tr>
<tr>
<td>db_ovref</td>
<td>Increment or decrement the reference count
for a big item.</td>
</tr>
<tr>
<td>db_pg_alloc</td>
<td>Indicates we allocated a page to a
database.</td>
</tr>
<tr>
<td>db_pg_free</td>
<td>Indicates we freed a page (freed pages are
added to a freelist and reused).</td>
</tr>
<tr>
<td>db_pg_freedata</td>
<td>Indicates we freed a page that still
contained data entries (freed pages are added
to a freelist and reused.)</td>
</tr>
<tr>
<td>db_pg_init</td>
<td>Indicates we reinitialized a page during a
truncate.</td>
</tr>
<tr>
<td>db_pg_sort</td>
<td>Sort the free page list and free pages at
the end of the file.</td>
</tr>
<tr>
<td>dbreg_register</td>
<td>Records an open of a file (mapping the
filename to a log-id that is used in
subsequent log operations).</td>
</tr>
<tr>
<td>fop_create</td>
<td>Create a file in the file system.</td>
</tr>
<tr>
<td>fop_file_remove</td>
<td>Remove a name in the file system.</td>
</tr>
<tr>
<td>fop_remove</td>
<td>Remove a file in the file system.</td>
</tr>
<tr>
<td>fop_rename</td>
<td>Rename a file in the file system.</td>
</tr>
<tr>
<td>fop_write</td>
<td>Write bytes to an object in the file
system.</td>
</tr>
<tr>
<td>ham_chgpg</td>
<td>Used to adjust a cursor location when a
Hash page is removed, and its elements are
moved to a different Hash page.</td>
</tr>
<tr>
<td>ham_copypage</td>
<td>Used when we empty a bucket page, but there
are overflow pages for the bucket; one needs
to be copied back into the actual
bucket.</td>
</tr>
<tr>
<td>ham_curadj</td>
<td>Used to adjust a cursor location when a
nearby record changes in a Hash
database.</td>
</tr>
<tr>
<td>ham_groupalloc</td>
<td>Allocate some number of contiguous pages to
the Hash database.</td>
</tr>
<tr>
<td>ham_insdel</td>
<td>Insert/delete an item on a Hash
page.</td>
</tr>
<tr>
<td>ham_metagroup</td>
<td>Update the metadata page to reflect the
allocation of a sequence of contiguous
pages.</td>
</tr>
<tr>
<td>ham_newpage</td>
<td>Adds or removes overflow pages from a Hash
bucket.</td>
</tr>
<tr>
<td>ham_replace</td>
<td>Handle updates to records that are on the
main page.</td>
</tr>
<tr>
<td>ham_splitdata</td>
<td>Record the page data for a split.</td>
</tr>
<tr>
<td>heap_addrem</td>
<td>Add or remove an entry from a Heap
database.</td>
</tr>
<tr>
<td>heap_pg_alloc</td>
<td>Indicates we allocated a page to a Heap
database.</td>
</tr>
<tr>
<td>heap_trunc_meta</td>
<td>Records the truncation of the meta page in
a Heap database.</td>
</tr>
<tr>
<td>heap_trunc_page</td>
<td>Records the truncation of a data page in a
Heap database.</td>
</tr>
<tr>
<td>qam_add</td>
<td>Describes the actual addition of a new
record to a Queue.</td>
</tr>
<tr>
<td>qam_del</td>
<td>Delete a record in a Queue.</td>
</tr>
<tr>
<td>qam_delext</td>
<td>Delete a record in a Queue with
extents.</td>
</tr>
<tr>
<td>qam_incfirst</td>
<td>Increments the record number that refers to
the first record in the database.</td>
</tr>
<tr>
<td>qam_mvptr</td>
<td>Indicates we changed the reference to
either or both of the first and current
records in the file.</td>
</tr>
<tr>
<td>txn_child</td>
<td>Commit a child transaction.</td>
</tr>
<tr>
<td>txn_ckp</td>
<td>Transaction checkpoint.</td>
</tr>
<tr>
<td>txn_recycle</td>
<td>Transaction IDs wrapped.</td>
</tr>
<tr>
<td>txn_regop</td>
<td>Logs a regular (non-child) transaction
commit.</td>
</tr>
<tr>
<td>txn_xa_regop</td>
<td>Logs a prepare message.</td>
</tr>
</tbody>
</table>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp164880"></a>Augmenting the Log for Debugging</h3>
</div>
</div>
</div>
<p>
When debugging applications, it is sometimes useful to
log not only the actual operations that modify pages, but
also the underlying Berkeley DB functions being executed.
This form of logging can add significant bulk to your log,
but can permit debugging application errors that are
almost impossible to find any other way. To turn on these
log messages, specify the --enable-debug_rop and
--enable-debug_wop configuration options when configuring
Berkeley DB. See <a class="xref" href="build_unix_conf.html" title="Configuring Berkeley DB">Configuring Berkeley DB</a> for more
information.
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp136104"></a>Extracting Committed Transactions and Transaction Status</h3>
</div>
</div>
</div>
<p>
Sometimes, it is helpful to use the human-readable log
output to determine which transactions committed and
aborted. The awk script, commit.awk, (found in the
db_printlog directory of the Berkeley DB distribution)
allows you to do just that. The following command, where
log_output is the output of db_printlog, will display a
list of the transaction IDs of all committed transactions
found in the log:
</p>
<pre class="programlisting">awk -f commit.awk log_output</pre>
<p>
If you need a complete list of both committed and
aborted transactions, then the script status.awk will
produce it. The syntax is as follows: </p>
<pre class="programlisting">awk -f status.awk log_output</pre>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp166064"></a>Extracting Transaction Histories</h3>
</div>
</div>
</div>
<p>
Another useful debugging aid is to print out the
complete history of a transaction. The awk script txn.awk
allows you to do that. The following command line, where
log_output is the output of the <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility and txnlist
is a comma-separated list of transaction IDs, will display
all log records associated with the designated transaction
ids:
</p>
<pre class="programlisting">awk -f txn.awk TXN=txnlist log_output</pre>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp171384"></a>Extracting File Histories</h3>
</div>
</div>
</div>
<p>
The awk script fileid.awk allows you to extract all log
records that refer to a designated file. The syntax for
the fileid.awk script is the following, where log_output
is the output of db_printlog and fids is a comma-separated
list of fileids:
</p>
<pre class="programlisting">awk -f fileid.awk PGNO=fids log_output</pre>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp183288"></a>Extracting Page Histories</h3>
</div>
</div>
</div>
<p>
The awk script pgno.awk allows you to extract all log
records that refer to designated page numbers. However,
because this script will extract records with the
designated page numbers for all files, it is most useful
in conjunction with the fileid script. The syntax for the
pgno.awk script is the following, where log_output is the
output of db_printlog and pgnolist is a comma-separated
list of page numbers:
</p>
<pre class="programlisting">awk -f pgno.awk PGNO=pgnolist log_output</pre>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp184088"></a>Other log processing tools</h3>
</div>
</div>
</div>
<p>
The awk script count.awk prints out the number of log
records encountered that belonged to some transaction
(that is, the number of log records excluding those for
checkpoints and non-transaction-protected operations).
</p>
<p>
The script range.awk will extract a subset of a log.
This is useful when the output of <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility is too
large to be reasonably manipulated with an editor or other
tool. The syntax for range.awk is the following, where
<span class="bold"><strong>sf</strong></span> and <span class="bold"><strong>so</strong></span> represent the LSN of the
beginning of the sublog you want to extract, and <span class="bold"><strong>ef</strong></span> and <span class="bold"><strong>eo</strong></span>
represent the LSN of the end of the
sublog you want to extract:
</p>
<pre class="programlisting"> awk -f range.awk START_FILE=sf START_OFFSET=so END_FILE=ef \
END_OFFSET=eo log_output </pre>
</div>
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