(B)0[mdb-wide-options-2 = qwq> [4mBUFFER[m [4mSIZE[m IS qqqqq> buffer-blocks qq> [4mBLOCKS[m qqqqqqwq> tq> [4mADJUSTABLE[m [4mLOCK[m [4mGRANULARITY[m IS qwqqq> [4mENABLED[m qqqwqqqu x mqqq> [4mDISABLED[m qqj x tq> [4mSNAPSHOT[m IS qqqqwqqqqq> [4mENABLED[m qwqq> [4mIMMEDIATE[m qwqwqu x x mqq> [4mDEFERRED[m qqj x x x mqqqqq> [4mDISABLED[m qqqqqqqqqqq>qqqqqqj x tq> [4mDICTIONARY[m IS qqqwqqq> [4mREQUIRED[m qqqqqqqwqqqqqqqqqqqqqu x tqqq> [4mNOT[m [4mREQUIRED[m qqqu x x tqqq> [4mUSED[m qqqqqqqqqqqu x x mqqq> [4mNOT[m [4mUSED[m qqqqqqqj x tq> [4mCARRY[m [4mOVER[m [4mLOCKS[m ARE qqwq> [4mENABLED[m qwqqqqqqqqqqqqqqqqu x mq> [4mDISABLED[m j x mq> [4mLOCK[m [4mTIMEOUT[m [4mINTERVAL[m IS number-seconds SECONDS qqqqqj
1 – buffer-blocks
The number of blocks Oracle Rdb allocates per buffer. Specify an
unsigned integer greater than zero. If you do not specify this
parameter, Oracle Rdb uses a buffer size that is three times the
PAGE SIZE value.
Buffer size is a global parameter and the number of blocks per
page (or buffer) is constrained to less than 64 blocks per page.
The page size can vary by storage area for multifile databases,
so you should determine the page size of each storage area based
on the sizes of records that will be stored in each storage area.
When you choose the number of blocks per buffer, choose a number
that is wholly divisible by all page sizes for all storage
areas in your multifile database. For example, if your database
has three storage areas with page sizes of 2, 3, and 4 blocks
respectively, choosing a buffer size of 12 blocks will ensure
optimal buffer utilization. If you choose a buffer size of 8, the
storage area with a page size of 3 blocks will waste 2 blocks per
buffer. Oracle Rdb reads as many pages as will fit into the buffer.
In this case, Oracle Rdb reads two pages of 3 blocks apiece into the
buffer, wasting 2 blocks.
2 – ADJUSTABLE_LOCK
Enables or disables whether or not the database system will
automatically maintain as few locks as possible on database
resources. The default is ENABLED, and results in fewer locks
against the database. However, if contention for database
resources is high, the automatic adjustment of locks can become a
CPU drain. Such databases can trade more restrictive locking for
less CPU usage by disabling adjustable lock granularity.
Disabling adjustable locking granularity may require that the
LOCKIDTBL, LOCKIDTBL_MAX, PQL_DENQLM, PQL_MENQLM OpenVMS SYSGEN
parameters for locks be increased.
3 – ENABLED-IMMEDIATE
The default, ENABLED IMMEDIATE causes read/write transactions
to write copies of records to the the snapshot file before
those records are modified, regardless of whether a read-only
transaction is active.
If you use the SNAPSHOT IS ENABLED clause to enable snapshots
on a multifile database, writing to all snapshot files for all
storage areas is enabled.
4 – ENABLED-DEFERRED
Specifies that read/write transactions not write copies of
records they modify to the snapshot file unless a read-only
transaction is active. Read-only transactions that attempt to
start after an active read/write transaction begins must wait for
all active read/write users to complete their transactions.
If you use the SNAPSHOT IS ENABLED clause to enable snapshots
on a multifile database, writing to all snapshot files for all
storage areas is enabled.
5 – DISABLED
Disables snapshot transactions. If you use the SNAPSHOT IS
DISABLED clause to disable snapshots on a multifile database,
writing to all snapshot files for all storage areas is disabled.
6 – DICTIONARY
The DICTIONARY IS [NOT] REQUIRED clause determines whether the
database must be invoked by path name for data definition changes
to occur. If you specify the DICTIONARY IS REQUIRED option,
the database must be invoked by path name to change metadata
and the data dictionary will be maintained. If you specify the
DICTIONARY IS NOT REQUIRED option, the database can be invoked by
either file name or path name to change metadata. The default is
DICTIONARY IS NOT REQUIRED.
The DICTIONARY IS [NOT] USED clause determines whether the
definition of the database and definitions of database elements
will be stored in the data dictionary. If you specify the
DICTIONARY IS USED option, the definition of the database and
definitions of database elements will be stored in the data
dictionary. If you specify the DICTIONARY IS NOT USED option,
no definitions will be stored in the data dictionary. The default
is DICTIONARY IS USED.
You receive an error message if you specify incompatible options,
such as the DICTIONARY IS REQUIRED option and the DICTIONARY IS
NOT USED option.
7 – CARRY_OVER_LOCKS
The carry-over locks option is a database-wide parameter
that allows you to disable carry-over lock optimization. This
optimization is enabled by default. Although this is an advantage
in more environments, it can result in false lock conflicts in
some applications.
The carry-over locks optimization holds area and record locks
across transactions and depends on NOWAIT transactions asking for
and acquiring the NOWAIT lock. This can result in long delays if
concurrent users are executing long verbs. You should consider
disabling the carry-over locks optimization if transactions
experience noticeable delays in acquiring the NOWAIT lock (as
seen in the output of the RMU/SHOW STATISTICS command). Note that
if you do disable the carry-over locks option, there may be some
performance degradation because transactions will acquire and
release area and top level ALG locks for every transaction.
8 – LOCK_TIMEOUT
Specifies the number of seconds for processes to wait during a
lock conflict before timing out. The number of seconds can be
between one and 65,000.
Sets the default database lock timeout interval. This is the
database wide timeout interval. It is used as the default as well
as the upper limit in determining the timeout interval to use.
For example, if LOCK TIMEOUT INTERVAL IS 25 SECONDS is specified
with the CHANGE DATABASE or DEFINE DATABASE statement, and a
user specifies 30 seconds with the SQL SET TRANSACTION WAIT 30
statement or sets the logical name RDM$BIND_LOCK_TIMEOUT_INTERVAL
to 30, RDO would still use the interval of 25 specified with the
LOCK TIMEOUT INTERVAL clause.