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HP NonStop Shadowbase Command Definitions

Database Specification Command Descriptions

HP NonStop Shadowbase Command Reference Manual—785421-002

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NOSTOPONMISSING or STOPONMISSING – If the CONS detects that

blocks (records) are missing from a target during replication,

STOPONMISSING will result in the CONS abending with an

appropriate EMS message to indicated the condition. It will not abend

if NOSTOPONMISSING is configured.

BUFFERED or WRITETHRUCACHE – WRITETHRUCACHE causes the

CONS to set this mode of I/O for the file in the file system. This results

in blocks being flushed to disk immediately after a CONS does an I/O

for a given block. BUFFERED will cause the file system to use the

disk cache and flush less frequently.

Notes: Because I/O is not done to the alternate key files, you will

need to load the alternate key files before making use of the target

files in an application program that uses the alternate key files.

Because unaudited/unstructured block-oriented I/O is used in this

mode of replication, there is a possibility that some data loss can

occur if the NonStop system crashes and it becomes necessary to

deploy a target on a backup NonStop system. The most reliable

configuration to use in order to minimize this data loss is to set

NODELAYFLUSH and WRITETHRUCACHE. Note that CONS I/O

throughput is less with these settings. The best performing

configuration is to set DELAYFLUSH and BUFFERED, but this has

the highest probability of data loss should a failover to a backup

system become necessary.

For partitioned files, there is a window of time where data may flow

into a subsequent partition before the prior partition is full. If a HP

Shadowbase failure occurs before all data arrives for the prior

partition and you need to switch to a backup system application,

there may be some data loss. Additionally, an application will not

be able to sequentially read the data in the secondary partition

unless the prior partition is repaired. The FIXESEQ program is

included that will repair incomplete partitions. It should be run prior

to deployment of the target file being used in an application. For

more information about FIXESEQ, reference the HP NonStop

Shadowbase Installation and Planning Manual section on this topic.

After running FIXESEQ and before deployment of a target in an

application, you should turn audit on using FUP. You should also

consider doing a TMFCOM DUMP FILES of the related entry-

sequenced files after audit is turned on and before deployment of

the files. This is a consideration because the I/O used by the

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HP Integrity NonStop H-Series Guida Utente Pagina 244

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