Monitoring Latches with Command-Line Utilities

You can use the following command-line utilities to obtain information about latches.

onstat -p

Execute onstat -p to obtain the values in the field lchwaits. This field stores the number of times that a thread was required to wait for a shared-memory latch.

Figure 17 shows an excerpt of sample onstat -p output that shows the lchwaits field.

...
ixda-RA  idx-RA   da-RA    RA-pgsused lchwaits
5        0        204      148        12
...

onstat -s

Execute onstat -s to obtain general latch information. The output includes the userthread column, which lists the address of any user thread that is waiting for a latch. You can compare this address with the user addresses in the onstat -u output to obtain the user-process identification number.

Figure 18 shows sample onstat -s output.

...
Latches with lock or userthread set
name     address  lock wait userthread
LRU1     402e90   0    0        6b29d8
bf[34]   4467c0   0    0        6b29d8
...