IBM 000-8697 Manual de usuario descargar pdf (Pagina 146)

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2-52 IBM Informix OnLine Database Server Administrator’s Guide

Shared-Memory Internal Tables

A byte lock is only generated if you are using VARCHAR data types. The byte

lock exists solely for rollforward and rollback execution, so you must be

working in a database that uses logging. Byte locks only appear in tbstat -k

output if you are using row-level locking; otherwise, they are merged with

the page lock.

Theupperlimitfor the maximum numberoflocks (speciﬁed as LOCKS inthe

conﬁguration ﬁle) is 256,000. The lower boundary for LOCKS is the number

of user processes (the current value of USERS) multiplied by 20.

Thenumberofentriesinthe lock hashtableisbasedonthenumberofentries

inthelockstable(speciﬁedasLOCKSintheconﬁgurationﬁle).Themaximum

number of hash values is the largest power of 2 that is less than the value

speciﬁed by the expression (LOCKS divided by 16). Each entry in the lock

hash table occupies 12 bytes.

OnLine Page-Cleaner Table

The page-cleaner table tracks the state and location of each of the page-

cleaner daemons, tbpgcl, that was speciﬁed during conﬁguration.

The page-cleaner table always contains 32 entries, regardless of the number

of page cleaners speciﬁed by CLEANERS in your conﬁguration ﬁle.

Each entry in the page-cleaner table occupies 20 bytes.

The upper limit for the maximum number of page cleaners (speciﬁed as

CLEANERSintheconﬁgurationﬁle)is32.ThelowerboundaryforCLEANERS

is 0.

When CLEANERS is set to 0, the tbinit daemon assumes responsibility for

page cleaning.When CLEANERS is setto any value greater than 0, thatis the

number of tbpgcl daemon processes managed by tbinit.

OnLine Tblspace Table

The tblspace table tracks all active tblspacesin theOnLine system.An active

tblspace is currently open to any OnLine user process. The count of active

tblspaces includes database tables, temporary tables, and internal control

tables, such as system catalog tables. Each active table receives one entry in

the active tblspace table. Entries in the tblspace table are tracked in an

associated hash table.

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