Blocked Sessions (b)

Blocked Sessions (b)

Blocked sessions are the silent killers of enterprise applications. No one notices there's a problem until the business is seriously affected. This is one of the most useful screens in ProTop as it can provide the user with detailed information on who is blocking whom, on what resource they are blocked, and if there is a chain of processes all blocked by the same user. You can also easily detect deadly embraces (deadlocks) using this screen.

In the above screen capture, you can see that user 54 (aptly named "victim") is blocked by user #56 (process ID 23372 on /dev/pts17) and is waiting for an exclusive lock on RECID 102 of table Feedback.

ProTop RT Label Alertable Metric* Description
Usr N/A User number of the user being blocked
Name N/A Login name of the user being blocked
PID N/A OS process ID of the session being blocked
Flags userFlags See below
Durati N/A Duration of the block
  zBlkDura This alertable field is not displayed and is the same as duration, but in seconds
Wait blkWait Lists what the user is waiting for, usually RECord. Followed by flags eXclusive, Queued, and/or Hold
Resrc Id blkResrc The ID, usually the RECord ID of the blocked resource
Table Blocker-Usr# etc. N/A See below
WaitList N/A User number(s) of all other users waiting for the same resource
  zBlkrQ This alertable field is not displayed and indicates how many users are blocked by this process

*Requires data collector "Blocked" in pt3agent.cfg. With the commercial version of ProTop, you can configure alerts using the metric names in this column. For a full list of metrics, see the Alertable Metrics section.

Blocker information

Provides detailed information on the user blocking this process.

Entry Description
Table The name of the table if the user is blocked waiting for a record
Blocker-Usr# User number of the blocking user
Device Device (shared memory) \ IP Address (remote client) of the blocking user
PID PID of the blocking user
Blocker-StatementCache If client statement cache is enabled, the line # and program name of the blocking user

Flag values

Flag Description
S Shared memory client
R Remote client
L Login broker
@ Server
H helper
O Other
4 4GL Client
W Webspeed client
B Batch client
A Application server
X Unknown
* Transaction active
d Disconnecting
r Undo or error
I STOP or Ctrl-c
N- Notification pending
-N Notification in process
NN Notification pending and in process