Hi Prasenjit,

In reviewing the log files you provided it appears that a request for merging branches had a query taking a long time to remove cache entries.  The alert time is 

And the query is below that ran for 8+ minutes.  There must have been some sort of lock because as soon as this query finished, the other requestors finished their processing, including the one identified in the requestor lock exception.  

"Database operation took more than the threshold of 500 ms: 510,442 ms SQL: DELETE FROM PEGACS_Rules.pr_sys_appcache_entry  WHERE pzinskey IN (SELECT e.pzinskey FROM PEGACS_Rules.pr_sys_appcache_dep d, PEGACS_Rules.pr_sys_appcache_entry e , PEGACS_Rules.pr_sys_app_hierarchy_flat h, PEGACS_Rules.pr_sys_app_hierarchy_flat h2, PEGACS_Rules.pr_sys_app_ruleset_index i, PEGACS_Rules.pr_sys_app_ruleset_index i2 , PEGACS_Rules.pr_sys_class_ancestors c, PEGACS_Rules.pr_sys_class_ancestors c1, PEGACS_Rules.pr_sys_class_ancestors c2 WHERE d.pzrulename = ? AND d.pzruletype = ? AND d.pzcacheconfigid = ? AND d.pzexplicitexcludecombined < 2 AND d.pzimplementationkey = e.pzimplementationkey AND e.pzapphash = h2.pztopapphash AND h2.pzapphash = i2.pzapphash AND i2.pzrulesetname = ? AND (i2.pzrulesetversionmajor = -1 OR (i2.pzrulesetversionmajor = ? AND (i2.pzrulesetversionminor = -1 OR i2.pzrulesetversionminor > ? OR (i2.pzrulesetversionminor = ? AND (i2.pzrulesetversionpatch = -1 OR i2.pzrulesetversionpatch >= ?))))) AND h.pztopapphash = h2.pztopapphash AND h.pzapphash = i.pzapphash AND i.pzrulesetname = d.pzrulesetname AND c.pxleafclassname = e.pzassembletimeleafclassname AND c.pxucclassname = d.pzappliestoclassname AND c1.pxleafclassname = e.pzassembletimeleafclassname AND c1.pxclassname = e.pzprimarypageclassname AND not(c1.pxheight > c.pxheight) AND c2.pxleafclassname = e.pzassembletimeleafclassname AND c2.pxclassname = ? AND not(c1.pxheight > c2.pxheight) AND (c.pxheight > c2.pxheight OR (c.pxheight = c2.pxheight AND ((d.pzrulesetname = ? AND (d.pzrulesetversionmajor = -1 OR (d.pzrulesetversionmajor = ? AND (d.pzrulesetversionminor = -1 OR (d.pzrulesetversionminor < ? OR (d.pzrulesetversionminor = ? AND d.pzrulesetversionpatch = -1 OR d.pzrulesetversionpatch <= ?))))) OR (d.pzrulesetname != ? AND (h.pzappheight > h2.pzappheight OR (h.pzappheight = h2.pzappheight AND i.pzrulesetindex > i2.pzrulesetindex ))))))) UNION ALL SELECT e.pzinskey FROM PEGACS_Rules.pr_sys_appcache_dep d, PEGACS_Rules.pr_sys_appcache_entry e , PEGACS_Rules.pr_sys_app_hierarchy_flat h, PEGACS_Rules.pr_sys_app_hierarchy_flat h2, PEGACS_Rules.pr_sys_app_ruleset_index i, PEGACS_Rules.pr_sys_app_ruleset_index i2 , PEGACS_Rules.pr_sys_class_ancestors c, PEGACS_Rules.pr_sys_class_ancestors c2 WHERE d.pzrulename = ? AND d.pzruletype = ? AND d.pzcacheconfigid = ? AND d.pzexplicitexcludecombined >= 2 AND d.pzimplementationkey = e.pzimplementationkey AND e.pzapphash = h2.pztopapphash AND h2.pzapphash = i2.pzapphash AND i2.pzrulesetname = ? AND (i2.pzrulesetversionmajor = -1 OR (i2.pzrulesetversionmajor = ? AND (i2.pzrulesetversionminor = -1 OR i2.pzrulesetversionminor > ? OR (i2.pzrulesetversionminor = ? AND (i2.pzrulesetversionpatch = -1 OR i2.pzrulesetversionpatch >= ?))))) AND h.pztopapphash = h2.pztopapphash AND h.pzapphash = i.pzapphash AND i.pzrulesetname = d.pzrulesetname AND c.pxleafclassname = d.pzassemblytimeclass AND c.pxucclassname = d.pzappliestoclassname AND c2.pxleafclassname = d.pzassemblytimeclass AND c2.pxclassname = ? AND (c.pxheight > c2.pxheight OR (c.pxheight = c2.pxheight AND ((d.pzrulesetname = ? AND (d.pzrulesetversionmajor = -1 OR (d.pzrulesetversionmajor = ? AND (d.pzrulesetversionminor = -1 OR (d.pzrulesetversionminor < ? OR (d.pzrulesetversionminor = ? AND d.pzrulesetversionpatch = -1 OR d.pzrulesetversionpatch <= ?))))) OR (d.pzrulesetname != ? AND (h.pzappheight > h2.pzappheight OR (h.pzappheight = h2.pzappheight AND i.pzrulesetindex > i2.pzrulesetindex ))))))))"

I would suggest you work with your DBA to ensure the proper indexes on the tables in question and run an analysis on the query for any optimizations.  If you need further assistance, please open up an SR.