IBM 000-8697 Manuale Utente

Utilities

The number of active users and the maximum number of users allowed are
also indicated. The maximum number of concurrent user processes is
specified as

USERS

 in the OnLine configuration file.

Use the -X option to obtain precise information about the processes that are
sharing and waiting for buffers.

For each buffer in use, the -X option displays general buffer information that
is also available with either the -b or -B option. See tbstat -b for an expla-
nation of these fields.

Unique to the -X option are the

sharers

 and

waiters

 fields. More than one

process can share data in a buffer. For each buffer, the

sharers

field lists the

addresses of all user processes sharing that buffer. During an update
operation, a process places an exclusive lock on a buffer and no sharing
occurs. In this situation, the

waiters

field lists the addresses of all user

processes waiting for the buffer.

The tbstat -b and -B options contain a

waitlist

field that displays the

address of the first user process waiting for the buffer. The -X option provides
a complete list of addresses for all waiting processes.

The maximum number of shared buffers is specified as

BUFFERS

 in the

OnLine configuration file.

wait

if the user process is waiting for a specific latch or lock, this
field displays the address of the resource. Use this address to
map to information provided in the -s (latch) or -k (lock)
output.

tout

is the lock time-out counter.

nlocks

is the number of locks that the user process is holding. (The -k
output should include a listing for each lock held.)

nreads

is the number of read calls that the user process has executed.
The reads could be either physical reads from disk or virtual
reads from the buffer cache.

nwrites

is the number of write calls that the user process has executed.
All write calls are writes to the shared-memory buffer cache.