Hi @Kapil ,
Welcome to Microsoft Q&A!
The steps in troubleshooting blocking as below, please get more details from Understand and resolve SQL Server blocking problems:
- Identify the main blocking session (head blocker)
- Find the query and transaction that is causing the blocking (what is holding locks for a prolonged period)
- Analyze/understand why the prolonged blocking occurs
- Resolve blocking issue by redesigning query and transaction
About SELECT queries blocks the REDO threads, please refer to Troubleshoot: Availability group exceeded RTO, see below:
Best regards,
Carrin
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