Avamar: SQL impact of running native SQL incremental backup on Avamar operations

Summary: This article describes how running SQL incremental backups natively from SQL Management Studio impacts Avamar SQL Backups. Because of this, Avamar incremental backups are expected to report a log gap due to a break in the log chain LSN sequence. ...

This article applies to This article does not apply to This article is not tied to any specific product. Not all product versions are identified in this article.
Check out other resources

Instructions

The following steps are designed to break the Avamar "log chain" sequence resulting in "log gap" errors:
  1. Perform a full backup followed by Avamar incremental backup. Keep a tab of the database entries in the sqlmeta.xml file.
  2. Perform a native SQL incremental backup on the Database forcing the LSN change on the SQL side. Keep a tab of Database entries in the sqlmeta.xml file.
  3. Now run Avamar incremental backup which is expected to report a log gap error on the Database. Here we notice that the entry from the sqlmeta.xml file gets removed. Deletion happens only for Policy driven incremental backups, If run on-demand incremental backup the entries in the sqlmeta.xml file are preserved.
Step #1:
  • Perform the following query from SQL Management Studio Query analyzer window to get "log sequence number" details.
SELECT msdb.dbo.backupset.database_name,
msdb.dbo.backupset.backup_start_date,
msdb.dbo.backupset.backup_finish_date,
msdb.dbo.backupset.type,
msdb.dbo.backupset.database_backup_lsn,
msdb.dbo.backupset.first_lsn,
msdb.dbo.backupset.last_lsn
FROM msdb.dbo.backupmediafamily
INNER JOIN msdb.dbo.backupset
ON msdb.dbo.backupmediafamily.media_set_id = msdb.dbo.backupset.media_set_id 
WHERE database_name IN ('test_db_1')
--and msdb.dbo.backupset.backup_finish_date between '1/20/2020' and '1/27/2020'
ORDER BY 
2 DESC,
3 DESC
Output of this query is shown below: 
database_name    backup_start_date    backup_finish_date    type   
database_backup_lsn    first_lsn    last_lsn
test_db_1    2020-02-12 16:37:31.000    2020-02-12 16:37:31.000    D   
34000000085100037    34000000089600037    34000000091300001
test_db_1    2020-02-05 20:29:23.000    2020-02-05 20:29:23.000    L   
34000000085100037    34000000083100001    34000000087600001
test_db_1    2020-02-05 20:28:55.000    2020-02-05 20:28:55.000    D   
34000000080600037    34000000085100037    34000000086800001
test_db_1    2020-02-05 20:17:30.000    2020-02-05 20:17:30.000    L   
34000000080600037    34000000078600001    34000000083100001
test_db_1    2020-02-05 20:17:02.000    2020-02-05 20:17:03.000    D   
34000000074600075    34000000080600037    34000000082300001
test_db_1    2020-02-05 11:53:18.000    2020-02-05 11:53:18.000    L   
34000000074600075    34000000050200075    34000000078600001
test_db_1    2020-02-05 11:52:50.000    2020-02-05 11:52:50.000    D   
34000000050200075    34000000074600075    34000000077800001
test_db_1    2020-02-04 15:05:18.000    2020-02-04 15:05:18.000    D    0   
34000000050200075    34000000053600001
Step #2:
  • Run Full Avamar backup on the Databases
  • Run query to check LSN numbers again
SELECT last_lsn, type, user_name FROM msdb..backupset WHERE
database_name=N'test_db_1' AND type LIKE 'L' ORDER by last_lsn DESC
Output of this query is shown below: 
last_lsn    type    user_name
34000000087600001    L    NT AUTHORITY\SYSTEM
34000000083100001    L    NT AUTHORITY\SYSTEM
34000000078600001    L    NT AUTHORITY\SYSTEM
Step #3:
  • Run Avamar Incremental backup
  • Check LSN numbers by running the below query
  • Verify that the backup_lsn from sqlmeta.xml matches to what the below query shows: 
SELECT last_log_backup_lsn FROM sys.database_recovery_status "WHERE database_id
= DB_ID(N'test_db_1')"
Output of this query is shown below: 
test_db_1    2020-02-12 16:44:40.000    2020-02-12 16:44:40.000    L   
34000000089600037    34000000087600001    34000000092500001
test_db_1    2020-02-12 16:37:31.000    2020-02-12 16:37:31.000    D   
34000000085100037    34000000089600037    34000000091300001
test_db_1    2020-02-05 20:29:23.000    2020-02-05 20:29:23.000    L   
34000000085100037    34000000083100001    34000000087600001
test_db_1    2020-02-05 20:28:55.000    2020-02-05 20:28:55.000    D   
34000000080600037    34000000085100037    34000000086800001
test_db_1    2020-02-05 20:17:30.000    2020-02-05 20:17:30.000    L   
34000000080600037    34000000078600001    34000000083100001
test_db_1    2020-02-05 20:17:02.000    2020-02-05 20:17:03.000    D   
34000000074600075    34000000080600037    34000000082300001
test_db_1    2020-02-05 11:53:18.000    2020-02-05 11:53:18.000    L   
34000000074600075    34000000050200075    34000000078600001
test_db_1    2020-02-05 11:52:50.000    2020-02-05 11:52:50.000    D   
34000000050200075    34000000074600075    34000000077800001
test_db_1    2020-02-04 15:05:18.000    2020-02-04 15:05:18.000    D    0      
             34000000050200075    34000000053600001
Step #4:
Step #5:
  • Run another Policy driven Avamar Incremental backup which is expected to generate the "log gap" error.
  • Rerun the LSN validation query
  • Check the logs to verify that backup fail with log gap error as shown in the snip below:
2020-02-12 16:58:01 avsql Info <19487>: Start checking for SMO DLL version
12...
2020-02-12 16:58:02 avsql Info <7065>: Working on target '(local)/test_db_1'
2020-02-12 16:58:03 avsql Info <40399>: Last full backup of target
'(local)/test_db_1' was found, labelnum = '45'.
2020-02-12 16:58:20 avsql Info <15765>: A log gap was identified or a full
backup was not found.
2020-02-12 16:58:20 avsql Error <40418>: Skipping database '(local)/test_db_1'
due to the following reason: A log gap was identified or a full backup was not
found.
2020-02-12 16:58:20 avsql Info <14245>: Creating a thread pool with 2 worker
threads.
2020-02-12 16:58:20 avsql Info <14275>: There is no more tasks to process.
2020-02-12 16:58:20 avsql Info <14271>: Waiting for worker threads to finish
...
2020-02-12 16:58:20 avsql Info <16256>: Creating process summary ...
2020-02-12 16:58:20 avsql Info <18493>: Status wrapup summary for all tragets
was processed.
2020-02-12 16:58:20 avsql Info <16257>: Inserted task: 0, completed: 0,
aborted: 0.
2020-02-12 16:58:20 avsql Info <16260>: Generating sql metadata ...
2020-02-12 16:58:20 avsql Error <14272>: There are no successfully finished
database tasks!
2020-02-12 16:58:20 avsql Error <14294>: An error occurred when generating sql
metadata
Run the query below to verify the break in LSN sequence 
SELECT last_log_backup_lsn FROM sys.database_recovery_status "WHERE database_id
= DB_ID(N'test_db_1')"
SQL query output to get the last_lsn information for Databases: 
database_name    backup_start_date    backup_finish_date    type   
database_backup_lsn    first_lsn    last_lsn
test_db_1    2020-02-12 16:52:42.000    2020-02-12 16:52:42.000    L   
34000000089600037    34000000092500001    34000000095800001
test_db_1    2020-02-12 16:44:40.000    2020-02-12 16:44:40.000    L   
34000000089600037    34000000087600001    34000000092500001
test_db_1    2020-02-12 16:37:31.000    2020-02-12 16:37:31.000    D   
34000000085100037    34000000089600037    34000000091300001
test_db_1    2020-02-05 20:29:23.000    2020-02-05 20:29:23.000    L   
34000000085100037    34000000083100001    34000000087600001
test_db_1    2020-02-05 20:28:55.000    2020-02-05 20:28:55.000    D   
34000000080600037    34000000085100037    34000000086800001
test_db_1    2020-02-05 20:17:30.000    2020-02-05 20:17:30.000    L   
34000000080600037    34000000078600001    34000000083100001
test_db_1    2020-02-05 20:17:02.000    2020-02-05 20:17:03.000    D   
34000000074600075    34000000080600037    34000000082300001
test_db_1    2020-02-05 11:53:18.000    2020-02-05 11:53:18.000    L   
34000000074600075    34000000050200075    34000000078600001
test_db_1    2020-02-05 11:52:50.000    2020-02-05 11:52:50.000    D   
34000000050200075    34000000074600075    34000000077800001
test_db_1    2020-02-04 15:05:18.000    2020-02-04 15:05:18.000    D    0      
             34000000050200075    34000000053600001
sqlmeta.xml file shows the last backup_lsn as: 34000000092500001: 
2020/02/12-21:58:20.86999 [avsql_assist]  avsql_metadata::avsql_metadata
sqlmetadata = '<sqlmetadata threadpool_size="2" version="1.1">
  <instance name="(local)">
    <database last_incremental_backup="1581525880" last_restore_backup="0"
backup_lsn="34000000092500001" last_differentail_backup="0" name="test_db_1"
is_system="false" last_full_backup="1581525451"
differential_base_lsn="34000000089600037">
      <backup_data stream_mark="stream" backup_lsn="34000000087600001"
av_group_replica="primary" num_vd_streams="1" name="f-0.test_db_1"
size="4915200" backup_time="1581525451">
        <file_group name="PRIMARY">
          <file file_type="Rows Data" physical_path="C:\Program Files\Microsoft
SQL Server\MSSQL13.MSSQLSERVER\MSSQL\DATA\test_db_1.mdf"
logical_name="test_db_1" />
        </file_group>
        <file file_type="Log" physical_path="C:\Program Files\Microsoft SQL
Server\MSSQL13.MSSQLSERVER\MSSQL\DATA\test_db_1_log.ldf"
logical_name="test_db_1_log" />
      </backup_data>
      <backup_data stream_mark="stream" backup_lsn="34000000092500001"
av_group_replica="primary" num_vd_streams="1" name="i-1.test_db_1"
size="655360" backup_time="1581525880">
        <file_group name="PRIMARY">
          <file file_type="Rows Data" physical_path="C:\Program Files\Microsoft
SQL Server\MSSQL13.MSSQLSERVER\MSSQL\DATA\test_db_1.mdf"
logical_name="test_db_1" />
        </file_group>
        <file file_type="Log" physical_path="C:\Program Files\Microsoft SQL
Server\MSSQL13.MSSQLSERVER\MSSQL\DATA\test_db_1_log.ldf"
logical_name="test_db_1_log" />
      </backup_data>
    </database>
  </instance>
</sqlmetadata>
Avamar Debug SQL logs snippet below shows that two LSN numbers from the SQL query and the sqlmeta.xml do not match: 
2020/02/12-21:58:20.87599 [avsql_assist]  <===
avsql_assist::evaluate_backup_lsn
2020/02/12-21:58:20.87599 [avsql_assist]  ===>
sqlconnectimpl_smo::get_last_backup_lsn
2020/02/12-21:58:20.87599 [avsql_assist]  retrieving last backup lsn for
'test_db_1' db from sys.database_recovery_status
2020/02/12-21:58:20.87599 [avsql_assist]  ===> sqlconnectimpl_smo::InitDll
2020/02/12-21:58:20.87599 [avsql_assist]  SMO dll already loaded.
2020/02/12-21:58:20.87599 [avsql_assist]  <=== sqlconnectimpl_smo::InitDll
2020/02/12-21:58:20.87899 [avsql_assist]  ==> SMOWrap::SMO_GetLastBackupLSN
2020/02/12-21:58:20.87899 [avsql_assist]  database 'test_db_1', last backup lsn
= '34000000095800001' 
2020/02/12-21:58:20.87899 [avsql_assist]  <===
sqlconnectimpl_smo::get_last_backup_lsn
2020/02/12-21:58:20.87899 [avsql_assist]  ===> avsql_metadata::get
2020/02/12-21:58:20.87899 [avsql_assist]  ===> avsql_metadata::get
2020/02/12-21:58:20.87899 [avsql_assist]  <=== avsql_metadata::get
2020/02/12-21:58:20.87899 [avsql_assist]  <=== avsql_metadata::get
2020/02/12-21:58:20.87899 [avsql_assist]  Last backup LSN: '34000000092500001',
Current LSN: '34000000095800001'
2020/02/12-21:58:20.87899 [avsql_assist]  ===>
avsql_assist::align_numeric_ustrings
2020/02/12-21:58:20.88000 [avsql_assist]  Before alignment - Str1:
'34000000092500001', Str2: '34000000095800001'
2020/02/12-21:58:20.88000 [avsql_assist]  After alignment - Str1:
'34000000092500001', Str2: '34000000095800001'
2020/02/12-21:58:20.88000 [avsql_assist]  <===
avsql_assist::align_numeric_ustrings
2020/02/12-21:58:20.88000 [avsql_assist]  Aligned before compare- Last backup
(metadata) LSN: '34000000092500001', Current (SQL Server) LSN:
'34000000095800001'
2020-02-12 16:58:20 avsql Info <15765>: A log gap was identified or a full
backup was not found.
2020/02/12-21:58:20.88199 [avsql_assist]  ===> sqlconnect::~sqlconnect
2020/02/12-21:58:20.89100 [avsql_assist]  <=== sqlconnect::~sqlconnect
2020/02/12-21:58:20.89100 [avsql_assist]  <===
avsql_assist::snapup_check_timestamps
2020-02-12 16:58:20 avsql Error <40418>: Skipping database '(local)/test_db_1'
due to the following reason: A log gap was identified or a full backup was not
found.

To resolve this failure and synchronize the LSN information, run a full backup for this Database.

Affected Products

Avamar Plug-in for SQL
Article Properties
Article Number: 000214572
Article Type: How To
Last Modified: 05 Sept 2025
Version:  2
Find answers to your questions from other Dell users
Support Services
Check if your device is covered by Support Services.