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< p > Library Version 11.2.5.2< / p >
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< th colspan = "3" align = "center" > DbEnv::set_memory_init()< / th >
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The DbEnv Handle
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< h2 class = "title" style = "clear: both" > < a id = "envset_memory_init" > < / a > DbEnv::set_memory_init()< / h2 >
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< pre class = "programlisting" > #include < db_cxx.h>
int
DbEnv::set_memory_init(DB_MEM_CONFIG object, u_int32_t count); < / pre >
< p >
This method sets the number of objects to allocate and initialize
for a specified structure when an environment is created. Doing
this helps avoid memory contention after startup. Using this
method is optional; failure to use this method causes BDB to
allocate a minimal number of structures that will grow dynamically.
These structures are all allocated from the main environment
region. The amount of memory in this region can be set via the
< a class = "xref" href = "envset_memory_max.html" title = "DbEnv::set_memory_max()" > DbEnv::set_memory_max()< / a >
method. If this method is not called then memory will be limited
to the initial settings or by the (deprecated) set maximum
interfaces.
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< p >
The database environment's initialization may also be configured
using the environment's < a href = "../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class = "olink" > DB_CONFIG< / a > file. The syntax of the entry
in that file is a single line with the string "set_memory_init",
one or more whitespace characters, followed by the struct
specification, more white space and the count to be allocated.
Because the < a href = "../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class = "olink" > DB_CONFIG< / a > file is read when the database environment
is opened, it will silently overrule configuration done before
that time.
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< p >
The < code class = "methodname" > DbEnv::set_memory_init()< / code > method must
be called prior to opening the database environment. It may be
called as often as needed to set the different configurations.
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< h3 class = "title" > < a id = "id3605780" > < / a > Parameters< / h3 >
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< h4 class = "title" > < a id = "id3605791" > < / a > struct< / h4 >
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The < span class = "bold" > < strong > struct< / strong > < / span > parameter must be
set to one of the following:
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< p > < a id = "envmem_DB_MEM_LOCK" > < / a >
< code class = "literal" > DB_MEM_LOCK< / code >
< / p >
< p >
Initialize locks. A thread uses this structure
to lock a page (or record for the QUEUE access
method) and hold it to the end of a transactions.
< / p >
< / li >
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< p > < a id = "envmem_DB_MEM_LOCKOBJECT" > < / a >
< code class = "literal" > DB_MEM_LOCKOBJECT< / code >
< / p >
< p >
Initialize lock objects. For each page (or record) which
is locked in the system, a lock object will be allocated.
< / p >
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< p > < a id = "envmem_DB_MEM_LOCKER" > < / a >
< code class = "literal" > DB_MEM_LOCKER< / code >
< / p >
< p >
Initialize lockers. Each thread which is active in a
transactional environment will use a locker structure
either for each transaction which is active, or for each
non-transactional cursor that is active.
< / p >
< / li >
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< p > < a id = "envmem_DB_MEM_LOGID" > < / a >
< code class = "literal" > DB_MEM_LOGID< / code >
< / p >
< p >
Initialize the log fileid structures. For each database handle
which is opened for writing in a transactional environment,
a log fileid structure is used.
< / p >
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< p > < a id = "envmem_DB_MEM_TRANSACTION" > < / a >
< code class = "literal" > DB_MEM_TRANSACTION< / code >
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< p >
Initialize transaction structures. Each active
transaction uses a transaction structure until it
either commits or aborts.
< / p >
< div class = "note" style = "margin-left: 0.5in; margin-right: 0.5in;" >
< h3 class = "title" > Note< / h3 >
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Currently transaction structures are not
preallocated. This setting will be used to
preallocate memory and objects related to
transactions such as locker structures and
mutexes.
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< p > < a id = "envmem_DB_MEM_THREAD" > < / a >
< code class = "literal" > DB_MEM_THREAD< / code >
< / p >
< p >
Initialize thread identification structures. If thread
tracking is enabled then each active thread will use a
structure. Note that since a thread does not signal the
BDB library that it will no longer be making calls, unused
structures may accumulate until a cleanup is triggered either
using a high water mark or by running
< a class = "xref" href = "envfailchk.html" title = "DbEnv::failchk()" > DbEnv::failchk()< / a > .
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< h4 class = "title" > < a id = "id3605653" > < / a > count< / h4 >
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The < span class = "bold" > < strong > count< / strong > < / span > parameter
sets the number of specified objects to initialize.
< / p >
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The < span class = "bold" > < strong > count< / strong > < / span > specified for
locks and lock objects should be at least 5 times the
number of lock table partitions. You can examine the
current number of lock table partitions configured for your
environment using the
< a class = "xref" href = "envget_lk_partitions.html" title = "DbEnv::get_lk_partitions()" > DbEnv::get_lk_partitions()< / a >
method.
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< h3 class = "title" > < a id = "id3605441" > < / a > Errors< / h3 >
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The < code class = "methodname" > DbEnv::set_memory_init()< / code > < span >
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method may fail and throw a < a class = "link" href = "dbexception.html" title = "Chapter > DbException< / a >
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
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< h4 class = "title" > < a id = "id3605024" > < / a > EINVAL< / h4 >
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If the method was called after < a class = "xref" href = "envopen.html" title = "DbEnv::open()" > DbEnv::open()< / a >
was called; or if an invalid flag value or parameter was specified.
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< a class = "link" href = "env.html" title = "Chapter > DbEnv< / a >
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< h3 class = "title" > < a id = "id3605871" > < / a > See Also< / h3 >
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< a class = "xref" href = "env.html#envlist" title = "Database Environments and Related Methods" > Database Environments and Related Methods< / a >
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