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Support Article

System Cleaner failing to clean pr_sys_context and pr_page_store

SA-78117

Summary



The following issues occur on Pega Platform 7.3:
  1. Socket time-out exception occurs and the SQL in a JAVA method in CleanupExpired fails.

    Predictive Diagnostic Cloud (PDC) ID - Socket Time-out (SocketTimeout-75)

  2. System Cleaner fails to clean pr_sys_context and pr_page_store.

    PDC ID- Conflicting Queries (DatabaseDeadlock-179)


Error Messages



PEGA0106 database deadlock detected. User 'pega' PID 13086 blocked by 'pega' PID 15764. Blocked statement was - delete from pegadata.pr_page_store where pxcreatedatetime < $1. Blocking statement was - delete from pegadata.pr_page_store where pyrequestorid in ( select pxrequestorid from pegadata.pr_sys_context where pxCreateDateTime < $1 )


Steps to Reproduce



Unknown


Root Cause



This is a feature of the database to either wait for a resource to be available or detect the presence of a cycle in the Wait list between two or more transactions that would result in a deadly embrace (never ending wait) unless one of the transactions is terminated.


Resolution



Here’s the explanation for the reported behavior:

The ClusterAndDBCleaner must be run on only one node, while the NodeCleaner must be run on all the nodes. 
The environment in this case runs 24/7 in terms of load. As a result, there is contention on the tables that are used for passivation and a deadlock occurs intermittently.

Ensure that the table content which is older than 7 days is not large.
Suggest Edit

Published May 7, 2019 - Updated October 8, 2020

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