What is DB block size?
DB_BLOCK_SIZE specifies (in bytes) the size of Oracle database blocks. Typical values are 4096 and 8192 . The value of this parameter must be a multiple of the physical block size at the device level. The value for DB_BLOCK_SIZE in effect at the time you create the database determines the size of the blocks.
How are gauge blocks calibration?
NIST master gauge blocks are calibrated by interferometry in accordance with the definition of gauge block length. Each master block carries a wringing layer with it, and this wringing layer is transferred to every block calibrated at NIST by mechanical comparison techniques.
How do I know my full DB size?
The size of the database is the space the files physically consume on disk. You can find this with: select sum(bytes)/1024/1024 size_in_mb from dba_data_files; But not all this space is necessarily allocated.
What is the block size for test tablespace?
Database/tablespace block size
| Block size | Maximum datafile size | Maximum database size |
|---|---|---|
| 2 K | 8,192 GB | 536 PB |
| 4 K | 16,384 GB | 1,073 PB |
| 8 K | 32,768 GB | 2,147 PB |
| 16 K | 65,536 GB | 4,294 PB |
Why do we have to perform frequent calibration of gauge blocks?
Like most test, measurement and inspection equipment, gage blocks require regular calibration to maintain accuracy. Scratches, gashes and other damage caused by wear and corrosion can negatively affect the blocks’ accuracy.
How do you calculate current undo retention?
For LOBs, the database attempts to honor the minimum undo retention period specified by UNDO_RETENTION . However, if space becomes low, unexpired LOB undo information may be overwritten. You can determine the current retention period by querying the TUNED_UNDORETENTION column of the V$UNDOSTAT view.
Can we change db block size?
The DB block size is one of the Oracle system parameters. The default DB block size cannot be changed once the database is created, but multiple DB block sizes can be set up to meet the requirement.
Can we change block size in Oracle?
You cannot modify the data block size after a database is created. You can only create a new database with the correct block size, export the old database and do a full import into the new database.
Why do gauge blocks wring together?
The source of the forces holding gage blocks together are thought to come from: Air pressure from the surrounding environment as the air is squeezed out when the blocks are slid together. Surface tension from oil that remains on the gage blocks or water vapor from the air that acts as an adhesive to hold them together.
What is slip gauge grade?
Slip gauges are made in five grades of accuracy. Calibration grade, grade 00, grade 0, grade I, and grade II, in the decreasing order of accuracy. The means to do so are ‘slip gauges’. They can be used to measure tolerances in the range of 0.001 to 0.0005 mm very accurately.
How do I find the size of a schema in SQL Server?
Using Table Sys.master_files
- SELECT sys.databases. name,
- CONVERT(VARCHAR,SUM(size)*8/1024)+’ MB’ AS [Total disk space]
- FROM sys.databases.
- JOIN sys.master_files.
- ON sys.databases.database_id=sys.master_files.database_id.
- GROUP BY sys.databases. name.
- ORDER BY sys.databases. name.
How does Oracle check a block?
Oracle checks a block by going through the data in the block, making sure it is logically self-consistent. Block checking can often prevent memory and data corruption. Block checking typically causes 1% to 10% overhead in most applications, depending on workload and the parameter value.
What is the performance overhead of block checking?
Block checking typically causes 1% to 10% overhead, depending on workload and the parameter value. The more updates or inserts in a workload, the more expensive it is to turn on block checking. You should set DB_BLOCK_CHECKING to FULL if the performance overhead is acceptable.
What should I do before setting the DB_block_checking parameter to true?
Before setting the db_block_checking parameter to TRUE, first execute the database verify (dbv)utility against the datafiles to make sure they are free of corruption. Even when db_block_checking=false, Oracle still provides block checking for the system tablespace.
How does Oracle check for index corruption?
FULL – all LOW and MEDIUM checks are performed, as well as semantic checks for index blocks (that is, blocks of subordinate objects that can actually be dropped and reconstructed when faced with corruption) Oracle checks a block by going through the data in the block, making sure it is logically self-consistent.