Kbase P6430: How to change database block size
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
3/7/2011 |
|
Status: Verified
GOAL:
How to change database block size
GOAL:
How to increase the block size for a database
FACT(s) (Environment):
All Supported Operating Systems
Progress 8.2x
Progress 8.3x
Progress 9.x
OpenEdge 10.x
FIX:
Progress V8.2 introduces a feature that enhances database performance: Database Variable-block Size.
At creation of a database, specify a database block size that is a multiple of 1024 Bytes. Specifically, 1024, 2048, 4096 and 8192 Bytes.
Previous to v8.2, Progress only created Databases with a blocksize of 1024Bytes (1k), regardless of the File System blocksize.
The fact that File Systems have different block sizes, added value the value of creating a progress database with a database blocksize the same as the File System blocksize.
By default, progress creates a database with a 1k blocksize.
The following lists the default File Systems and their system blocksize.
OS Blocksize V7 DB Blocksize
----------------------------------------
UNIX (most) 1024bytes (1k) 1024Bytes (1k)
NT 4096 (4k) 4096Bytes (4k)
VMS 512 (.5k) 1024Bytes (1k)
DOS 1024 (1k) 1024Bytes (1k)
SEQUENT 2048 (2k) 2048Bytes (2k)
CREATING A MULTI-VOLUME DATABASES:
prostrct create <dbname> <dbname.st> -blocksize <num>
where -blocksize <num>
1024
2048
4096
8192
-blocksize must be the last argument on the command line.
CREATING A SINGLE VOLUME DATABASES:
prodb <dbname> $DLC/empty1
..... empty2
..... empty4
..... empty8
procopy $DLC/empty1 <dbname>
... empty2 <dbname>
... empty4 <dbname>
... empty8 <dbname>
DATABASE BUFFERS (-B) AND VARIABLE BLOCKSIZE DATABASES
The -B parameter is used to define the number of database blocks to be loaded in the database buffer pool at startup of the database broker. If your database was created with the default blocksize of 1k, (prior to Version 8.2) the database buffer pool (-B) will be in 1k increments. If a database has been created with a blocksize of 2k, 4k or 8k, then the database buffer pool (-B) will be in the
increments of 2k, 4k or 8k, respectively. You can display this from the promon utility in R&D,option 1, option 14 Shared Memory Segments.
The following, lists Shared memory segment sizes from different Database block sizes on an HP-UX 10.10. Note the segment size is slightly larger than the blocksize multiplied by the (-B 1000).
The point here is to be aware that the amount of memory increases (-B) parallel to the size of the database blocksize.
Example: proserve <dbname> -B 1000
Shared Memory Alloc. x (-B) = Segment Size
DB Blocksize(bytes) Shared Memory Alloc(bytes) Segment Size(bytes)
----------------------------------------------------
1024 1380 1413120
2048 2432 2490368
4096 4540 4648960
8192 8756 8966144
DISADVANTAGES:
1. There is no conversion utility available to convert from one database blocksize to another. You must DUMP and LOAD the database into a new structure.
2. You cannot use the procopy or prorest command to a database of a different blocksize. You will receive the following error:
Source and Target databases should have same blocksize: 1024, 4096
3. Your database will use more disk space moving to a variable length blocksize. For example, converting a database with 100 records from a 1k to an 8k blocksize produces the following results:
1k blocksize : 100rec/32rec per block = 3.125(or 4blks) x 1k = 4k
8k blocksize : 100rec/64rec per block = 1.563(or 2blks) x 8k = 16k
ADVANTAGES:
1. It has been increasingly noticed that a larger blocksize than 1k are becoming available on many OS platforms. There are performance improvements in moving to blocksizes that are equal to or a multiple of the underlying filesystem's block size.
2. There are underlying physical differences between 1k, 2k, 4k and 8k database blocksizes. The record manager will manage 64 records per block with an 8k blocksize database and 32 records per block with a 1k, 2k and 4k blocksize database. Thus. reducing the amount of i/o required to access records both through an index and sequentially..