IBM 000-8697 Manual do Utilizador descarregar pdf (Página 145)

100

101

System Architecture 2-51

Shared-Memory Internal Tables

The minimum value of DBSPACES is 1, representing the root dbspace.

OnLine Latch Table

Thelatch table isnota table inthesame sense asothertables, but itfunctions

in a similar manner to track all latches in the OnLine system. Refer to

page 2-41foradetaileddiscussionofhowOnLineuseslatchestocontroland

manage modiﬁcations to OnLine shared memory.

The number of latch entries is equal to the number of shared-memory

resources conﬁgured for the OnLine system. As OnLine administrator, you

cannot modify the number of latches.

You can obtain information about latches from the tbstat -s output. You can

use the user process information from the tbstat -u output to determine if a

user process is holding a latch.

OnLine Lock Table

The lock table represents the pool of available locks. Each entry in the lock

table represents one lock. A single transaction can own multiple locks. A

single user process is limited to 32 concurrent table locks. The lock table

includes an associated hash table.

When an entry in the lock table is used, a lock is created. The information

stored in the table describes the lock. The lock description includes the

following four items:

■ The address of the user process that owns the lock

■ The type of lock (exclusive, update, shared, byte, or intent)

■ The page and/or rowid that is locked

■ The tblspace where the lock is placed

The number of entries in the lock table is equal to the maximum number of

locksinthisOnLinesystem,speciﬁedasLOCKSintheconﬁgurationﬁle.Each

entry in the lock table occupies 32 bytes.

Refer to IBM Informix Guide to SQL: Tutorial for an explanation of locking and

SQL statements. Refer to page 2-38 for a detailed explanation of the effect of

locks on buffer management. Refer to page 7-88 for information on

monitoring locks with tbstat -k.

1 2 ... 140 141 142 143 144 145 146 147 148 149 150 ... 701 702

Comentários a estes Manuais

Sem comentários

IBM 000-8697 Manual do Utilizador Página 145

Comentários a estes Manuais

Manuais e produtos relacionados com Software de bases de dados IBM 000-8697