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|
|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.
Provides detailed information on the user blocking this process.
|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|
|S||Shared memory client|
|r||Undo or error|
|I||STOP or Ctrl-c|
|-N||Notification in process|
|NN||Notification pending and in process|