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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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first record read that matches both the length of the target record

and the contents of the before image (if DBS BEFOREVALUES is

ON) will be updated. All other records will be ignored. If DBS

BEFOREVALUES is disabled, only the record lengths are checked.

If no records are found along the alternate key path that matches

the criteria, a message is logged (depending on the level of

messages). If INSERTNOTFOUND is set, the update is converted

to an insert. Otherwise the update is ignored.

If the DBS BEFOREVALUES are enabled, the source’s “before”

value of the alternate key fields is used for positioning. Hence,

BEFOREVALUES should normally be ON. However, setting the

BEFOREVALUES to ON increases the data replication traffic as

now both the before and the after values are replicated for an

UPDATE (otherwise, only the after values are replicated). You can

turn BEFOREVALUES to OFF (the default) if you are sure that your

application does not change the alternate key file values. When

BEFOREVALUES is set to OFF, HP Shadowbase uses the

source’s after image key values for positioning: if the update

changes the alternate key portion of the file, the wrong record may

be selected for update on the target, and target database corruption

will result. If the alternate key value can change, then

BEFOREVALUES of the DBS should be set to ON.

Also note the that contents of each record read is compared to the

before image only if BEFOREVALUES is ON. If you disable

BEFOREVALUES, the first record read whose length matches that

of the source record will be updated, possibly leading to the wrong

record being updated on the target. Only disable BEFOREVALUES

if you know the source application updates the first matching record

length along this key path. In most cases, it is safest to leave

BEFOREVALUES ON.

An update on the source for a record that does not exist on the

target will only be convert to an insert if the INSERTNOTFOUND

DBS settting is turned ON. Otherwise a message will be logged

and the update will be ignored.

Note: Bit0 is the least significant bit in the integer number (the “ones” bit)

and Bit5 to Bit15 are reserved for future use.

BEFOREVALUES { ON }

{ OFF }

Initial Changed

Version Version Values Default Minimum Maximum Alter

1 2 ... 227 228 229 230 231 232 233 234 235 236 237 ... 345 346

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