Monitoring Locks

You can view the lock table with onstat -k. Figure 39 shows sample output for onstat -k.

Locks
address  wtlist   owner    lklist   type     tblsnum  rowid    key#/bsiz
300b77d0 0        40074140 0        HDR+S    10002    106        0
300b7828 0        40074140 300b77d0 HDR+S    10197    123        0
300b7854 0        40074140 300b7828 HDR+IX   101e4    0          0
300b78d8 0        40074140 300b7854 HDR+X    101e4    102        0
 4 active, 5000 total, 8192 hash buckets 

In this example, a user is inserting one row in a table. The user holds the following locks (described in the order shown):

• A shared lock on the database
• A shared lock on a row in the systables system catalog table
• An intent-exclusive lock on the table
• An exclusive lock on the row

To determine the table to which the lock applies, execute the following SQL statement. For tblsnum, substitute the value shown in the tblsnum field in the onstat -k output.

SELECT tabname 
FROM systables
WHERE partnum = hex(tblsnum)

You can also query the syslocks table in the systables database to obtain information on each active lock. The syslocks table contains the following columns.

Column

Description

dbsname

Database on which the lock is held

tabname

Name of the table on which the lock is held

rowidlk

ID of the row on which the lock is held (0 indicates table lock)

keynum

The key number for the row

type

Type of lock

owner

Session ID of the lock owner

waiter

Session ID of the first waiter on the lock