Parameter DASO= on X_RUN command
|Date:||22 June, 1999|
|Product/Release:||LANSA for Windows|
|Abstract:||The Data Area Storage Option parameter allows you to emulate data area value storage and locking using flat files|
|Submitted By:||LANSA Technical Support|
|Last Review:||November 2010|
The DASO (Data Area Storage Option) parameter may be set to D or F. D indicates that data area value storage and locking should be emulated using table LX_DTA and the standard LOCK_OBJECT/UNLOCK_OBJECT logic. D is the default value. F indicates that data area value storage and locking should be emulated using flat operating system files stored in the same directory as any relative record number assignment files (refer to the RPTH= parameter). Locking and unlocking is achieved by using the appropriate operating system facilities for low level file access.
The guidelines, rules and limitations that apply when using the DASO=F parameter are:
- This option is ignored in Windows 16 bit applications.
- Generally this option is faster and uses less system resources than the DASO=D option.
- This option causes the data area value to be stored in a file named <data area>.ARA in the same directory as the relative record number assignment files (.RRN) are stored. Refer to the RPTH= parameter for details of how this directory name is defaulted and specified. The file names used are reflective of the uppercase data area name, so data area names of more than 8 characters will cause file names of more than 8 characters to be created.
- Ensure that all data area names used conform to AS/400 object naming standards which mean that the first character must be one of A ->Z (uppercase), $, @ or # followed by up to 9 more characters that must be one of A ->Z (uppercase), 0 -> 9, $, @ or #. No other characters are permitted. Failure to observe this rule may lead to application failure and/or unexpected results.
- Locking is accomplished by using the appropriate operating system file access facilities. This means that data areas that are left locked (e.g. via the GET_CHAR_AREA built in function) leave an operating system file handle open until such time as they are unlocked or the application terminates. Some operating systems impose a limit on the number of open file handles that will be allowed at any one time which may limit how many locked data areas can actually be concurrently locked. It is recommended not to have more than 4 concurrently locked data areas.
- The use of the option to divert data area accesses to a server system when running applications in super-server mode takes precedence over this option. Normally only standalone systems and server systems use this option. Clients connected by LANSA super-server facilities do not normally use this option, relying instead on the super-server connection option to divert their data area access requests to the server system automatically. The server system itself then may choose to use DASO=F to further divert incoming client requests into flat files rather than the DBMS table LX_DTA.
- Use caution when switching between the DASO=D (the default) and DASO=F options. Those data area values stored in table LX_DTA and those stored in <data area>.ARA files must have their current values aligned each time such a switch occurs. The value alignment process the responsibility of the user.