IBM 000-8697 Manuale Utente Scaricare il pdf (Pagina 111)

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System Architecture 2-17

What Happens During Disk-Space Initialization

Next, tbinit reserves space in the initial chunk of the root dbspace for the

physicalandlogicallogs.Aspartofthesamestep,tbinitupdatesthepointers

in shared memory with the new disk addresses. The daemon repeats this

process for each disk structure. In each pass, tbinit reads conﬁguration

values from its private data space, creates a structure and then updates any

associated structures in shared memory with required address information.

If mirroring is enabled and a mirror chunk is speciﬁed for the root dbspace,

spaceforthemirrorchunkisreservedduringthisprocess.Inthisway,shared

memory is initialized structure by structure.

Next, tbinit initializes the tblspace tblspace, which is theﬁrst tblspace in the

rootdbspace.Thetblspacetblspacesize is calculated fromthesizeofthe root

dbspace. (Refer to page 2-104 for further information about the tblspace

tblspace.)

The database tblspace is initialized next. (Refer to page 2-107 for further

information about the database tblspace.)

Step 6: Wake Parent tbinit Process

After the tbinit daemon builds the database tblspace, it wakes the parent

tbinit processandwritesan“initializationcomplete” message in theOnLine

message log (speciﬁed as MSGPATH in the conﬁguration ﬁle). The prompt

returns to the user at this point. Any error messages that might have been

passed from the daemon to the parent process are displayed, either at the

UNIX command line or within DB-Monitor. The parent process goes away at

this point. Its role is ended.

Step 7: Initiate First Checkpoint

Next, the tbinit daemon beginsthe ﬁrstOnLine checkpoint. Data buffers are

ﬂushed, including the logical log and physical log buffers. The daemon

creates a unique indexfor the database tblspace on the columnthat contains

database names and continues with the checkpoint. (The index is used later

to ensure that all database names are unique.) After the checkpoint

completes, the daemon writes a “checkpoint complete” message in the

OnLine message log. (Refer to page 2-70 for further information about

checkpoints.)

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IBM 000-8697 Manuale Utente Pagina 111

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