IBM 000-8697 ユーザーズマニュアル

IBM Informix OnLine Database Server Administrator’s Guide

Monitor shared memory (tbstat -o) to capture a static snapshot of OnLine
shared memory that you can use for analysis and comparison.

Monitor latches to determine if a user process is holding a latch or if
contention of shared-memory resources exists.

From the command line, execute tbstat -o to save a copy of the shared-
memory segment. You can execute tbstat -o with a filename parameter to
specify the file to contain the output. Otherwise, the output is saved to
tbstat.out

 in the current directory. The shared-memory segment file is the

same size as the shared-memory segment. The size of shared memory is
displayed in the tbstat header. After you save a copy of shared memory to a
file, you can execute other tbstat options using the filename as a parameter.
If you do, the tbstat information is derived from the shared-memory segment
stored in the specified file. Refer to

. Refer to

 for further information about tbstat filename

syntax and use.

Execute tbstat -p to obtain the value in the field

lchwaits

, which is the

number of times a user process (any process) was required to wait for a
shared-memory latch. A large number of latch waits typically results from a
high volume of processing activity in which most of the transactions are
being logged. (The number of latches is not configurable and cannot be
increased.) Refer to

when you execute tbstat -p.

Execute tbstat -s to obtain general latch information. The output lists the
address of any user process waiting for a latch. You can compare this address
with the users’ addresses in the tbstat -u output to obtain the user process
identification number. Never kill a database server process that is holding a
latch. If you do, OnLine immediately initiates an abort. Refer to

for

a complete listing of all fields that display when you execute tbstat -s.