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Extracting Metrics from MSlogreader_history - "Approximately 45000000 log records have been scanned..."
by BF (Senior MSSQL Operations - Enterprise, Cloud, Strategy)

Extracting metrics from Distribution.dbo.MSlogreader_history messages "Approximately 45000000 log records have been scanned in pass # 4, 0 of which were marked for replication."

What % of total log records scanned are marked for replication?

What are the total commands delivered over each delivery interval?

The below script provides insights into a system under heavy insert/update/delete activity, but very little of the Publisher Database Transaction Log Records are marked for replication. If high # records being scanned and a low % are marked for replication, common options to improve Log Reader throughput are increase the ReadBatchSize of the agent, perform re-indexing during maintenance window or re-architect replication and place the articles into their own database if your setup has few tables out of many configured for replication.

t1.agent_id as 'AgentID', as 'Agent Name',
Convert(int,delivered_commands - LAG(delivered_commands, 1,0) OVER (ORDER BY YEAR([time]))) AS 'Commands Added',
Substring(comments,Charindex('y',comments)+1, Charindex('log ',comments)-14) as 'Log Records Scanned',
LAG(Substring(comments,Charindex('y',comments)+1, Charindex('log ',comments)-14),1,0) OVER (ORDER BY YEAR([time])) as 'Previous Log Records Scanned',
Convert(Decimal(18,3),Convert(Decimal(18,3),(delivered_commands - LAG(delivered_commands, 1,0) OVER (ORDER BY YEAR([time]))+1)) / Convert(Decimal(18,3),(LAG(Substring(comments,Charindex('y',comments)+1, Charindex('log ',comments)-14),1,0) OVER (ORDER BY YEAR([time]))+1)) * 100)
as '% All T-Log Records marked for REPL'
Into #TMP
from Distribution.dbo.MSlogreader_history t1 with (nolock)
inner join Distribution.dbo.MSlogreader_agents t2 with (nolock)
on t1.agent_id =
where t1.agent_id = 8
and comments like '%marked for replication%'
order by time asc
Select * from #TMP where [% All T-Log Records marked for REPL] < 100.00
Drop Table #TMP