Caché Monitoring Guide
Monitoring Block Collisions Using ^BLKCOL
[Back] [Next]
   
Server:docs2
Instance:LATEST
User:UnknownUser
 
-
Go to:
Search:    

A block collision occurs when a process is forced to wait for access to a block. Excessive block collisions slow application performance.

Using ^BLKCOL
The ^BLKCOL utility samples block collisions over a specified period (10 seconds by default), recording the latest block collision within a specified interval (10 milliseconds by default) during this time. For each recorded collision, ^BLKCOL identifies not only the block, but the global involved and its first and last references in the block, as well as the routine and line that created the process attempting to access the block.
Note:
The cstat -D option, as described in Running cstat with Options in the “Monitoring Caché Using the cstat Utility” appendix of this guide, also samples block collisions, but identifies only the blocks involved.
The output of cstat -D is included in the reports generated by the ^pButtons utility, as described in the Monitoring Performance Using ^pButtons chapter of this guide.
When running ^BLKCOL, you can specify the following:
^BLKCOL Ouput
Use of the ^BLKCOL utility is shown in the following sample terminal session:
%SYS>d ^BLKCOL

Block Collision Analysis

How many seconds should we sample: <10>
How long to wait (ms) between each sample: <10>
Collect routine details? <Y>
Format for 'T'op counts, 'D'isplay all, 'S'orted CSV, 'H'ot spot, or 'R'aw CSV: <T>
Number of blocks to display: <10>
Output to file: <0>

Sampling ... (any key to interrupt)


625 block collisions in 735 samples.

Block # (count) - Global refs (first - last in block) - Routine refs (SFN)

767       (395) in c:\mycache\mgr\user\
  ^acctest - ^acctest(10220," 167") (T/BPtr)
    325 at ^AccessTest+156(4)
    25 at ^AccessTest+121(4)
    24 at ^AccessTest+92(4)
    8 at ^AccessTest+109(4)
    8 at ^AccessTest+127(4)
    4 at ^AccessTest+170(4)
    1 at ^AccessTest+163(4)

3890      (11)  in c:\mycache\mgr\user\
  ^acctest(2552,"  371") - ^acctest(2552,"  38") (Data)
    6 at ^AccessTest+164(4)
    3 at ^AccessTest+163(4)
    1 at ^AccessTest+134(4)
    1 at ^AccessTest+156(4)

15572     (9)   in c:\mycache\mgr\user\
  ^acctest(6980," 4795") - ^acctest(6988," 3259") (Data)
    7 at ^AccessTest+134(4)
    1 at ^AccessTest+164(4)
    1 at ^AccessTest+170(4)

15818     (8)   in c:\mycache\mgr\user\
  ^acctest(9124," 173") - ^acctest(9124," 1743") (Data)
    5 at ^AccessTest+164(4)
    3 at ^AccessTest+170(4)

971       (7)   in c:\mycache\mgr\user\
  ^acctest(484," 3927") - ^acctest(484," 3938") (Data)
    5 at ^AccessTest+170(4)
    2 at ^AccessTest+164(4)

1137      (7)   in c:\mycache\mgr\user\
  ^acctest(756," 4063") - ^acctest(756," 4073") (Data)
    3 at ^AccessTest+109(4)
    2 at ^AccessTest+134(4)
    1 at ^AccessTest+156(4)
    1 at ^AccessTest+163(4)

2999      (7)   in c:\mycache\mgr\user\
  ^acctest(2092,"  666") - ^acctest(2092,"  674") (Data)
    3 at ^AccessTest+170(4)
    1 at ^AccessTest+109(4)
    1 at ^AccessTest+121(4)
    1 at ^AccessTest+134(4)
    1 at ^AccessTest+164(4)

6173      (7)   in c:\mycache\mgr\user\
  ^acctest(3684,"  528") - ^acctest(3684,"  536") (Data)
    3 at ^AccessTest+163(4)
    1 at ^AccessTest+109(4)
    1 at ^AccessTest+156(4)
    1 at ^AccessTest+164(4)
    1 at ^AccessTest+170(4)

14617     (7)   in c:\mycache\mgr\user\
  ^acctest(9688,"   18") - ^acctest(9688,"   26") (Data)
    4 at ^AccessTest+170(4)
    2 at ^AccessTest+164(4)
    1 at ^AccessTest+134(4)

15282     (7)   in c:\mycache\mgr\user\
  ^acctest(8700," 4889") - ^acctest(8760," 1402") (Data)
    4 at ^AccessTest+170(4)
    3 at ^AccessTest+164(4)
%SYS>d ^BLKCOL

Block Collision Analysis

How many seconds should we sample: <10>
How long to wait (ms) between each sample: <10>
Collect routine details? <Y>
Format for 'T'op counts, 'D'isplay all, 'S'orted CSV, 'H'ot spot, or 'R'aw CSV: <T> H
Number of blocks to display: <10>
Output to file: <0>

Sampling ... (any key to interrupt)


571 block collisions in 768 samples.

 
Sorted by routine/line that waits for block ownership
_____________________________________________________

(571) AccessTest
    (324) +156^AccessTest :  s @G@($J,node)=$$getdata($E(Str,1,$r(1000)))  ;SMLXXX+, AFH
    (54) +164^AccessTest :  k @G@($J,node)
    (43) +134^AccessTest :  .  k @G@($J,node)
    (31) +92^AccessTest :  .  .  k @G@($j)
    (28) +109^AccessTest :  .  s x=$O(@G@($J,x))

Sorted by routine that owns the block
_____________________________________

(472) AccessTest
    (472) +AccessTest