Best practice to identify the blocking sql statement from Real Time window instead of the History window:
1) Under History option based on your screenshot, there are no Sids
that gets retained that correlates with the blocking sqls.
This is by designed.
The user could only narrow down to the time when she/he thought there
is a blocking sqls under History.
2) However, under Real Time option next to the History option
from the Performance Analysis GUI client, this does retain the Sids of the
blocking sql which helps to identify the blocking sql statement in the Real time mode.
In Real-Time mode, the Blocking Locks tab displays all
locks that have occurred and are occurring in the current
period. This tool facilitates an at-a-glance,
in-depth viewing of system locking activity. Use it to
identify sessions causing excessive lock problems.
Expanding the blocking session by clicking on the + icon displays the set of individual
locks created by the blocking session. Only locks which actually resulted in a block are
included. The lock icon indicates a currently active lock.
The displayed metrics are as follows:
Agent ID - Agent ID of the blocked session. Click the Agent ID to drill down
into the blocked session and trace its activity.
Database - The database where the blocked session is running.
Mode Wanted - The blocking mode for a SQL statement that is currently blocked
Lock Type - Type of blocking lock.
Lock Time - Date and time when the blocking began.
Lock Status - Status of blocking lock.
Locked Server PID - The Process Identification (PID) of the blocked session.
The user could also click on F1 function key on the Window where locks are located to get more information.