Re: How to retrieve the data compression method of a save file?

On 11-Feb-2016 08:18 -0700, rob wrote:

On 11-Feb-2016 08:01 -0700, Szepesi Frigyes wrote:

On 10-Feb-2016 06:11 -0700, Vernon Hamberg wrote:

To the original poster - there has to be something in the SAVF
that would tell you this. SAVFs can be read record by record, and
there might be something in the OIR of the object. <<SNIP>>

I tried to dump 3 save files I created with different DTACPR
settings. Dumps do not tell me anything,
but I also copied those save files to the IFS with CPYTOSTMF
command. In the files with *MEDIUM and *HIGH I saw two suspicious
strings at the same position:L D_TRS (for *MEDIUM,uses TERSE
algorythm) and LD_LZ1 (for *HIGH, uses LZ1 algorythm) I could not
see anything for files without or with LOW compression.

I wonder if IBM would create a new SQL based "IBM i Services",

"Storage Services" for this? Perhaps QSYS2.SAVE_FILE_ATTRIBUTES?
That column would have values for:
- No compression
- Low compression
- Medium compression
- High compression
and they could use internal APIs to retrieve the inforation you're
seeing in DMPOBJ.
<<SNIP>>

The Dump Object (DMPOBJ) does not dump any of the Dump Space data
records. The OP used the Copy To Stream File (CPYTOSTMF) to get the binary
data /records/ from the Dump Space into a Stream File (STMF) [though the
data could have been copied to a database file or to a User Space (USRSPC)
instead].

IMO the more appropriate approach would be to ask that the List Save
File (QSRLSAVF) API be updated to include the type of compression; anyone
could then create their own tooling, and that which is not limited only to
what the SQL [services] might provide.

Because the copied data can be effectively
disassembled\reverse-engineered [others have already done much of that
already over the years, so examples may exist on the web], knowing exactly
what offset to look for the compression-type could probably be found
predictably; of course fully dependent upon the implementation by the OS
which is subject to change [and why getting the info from the appropriate
API is more, IMO most, appropriate].

--
Regards, Chuck

--
This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list
To post a message email: MIDRANGE-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/midrange-l
or email: MIDRANGE-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/midrange-l.

Please contact support@xxxxxxxxxxxx for any subscription related
questions.