#125: xdb vs op2 in Nastran

xdb: Entry: PARAM,POST,0
Results are accessed through Direct Results Access (DRA) working directly with MSC Nastran results database
1) xdb files are compatible primarily with Patran and other MSC Software.
2) Time to read the xdb results into the Patran database is eliminated (accessed directly from Nastran result database).
3) Since the .xdb data is not duplicated in the Patran database, the size of the Patran database is greatly reduced.
4) Multiple xdb files can be accessed from a single Patran database and can be well managed, since the subcases of each xdb can be easily distinguished from one another.
5) xdb file size limit can go up to 8-10GB.
6) xdb files can only be accessed when they are located on the same machine that Patran is running.
7) Deleting a single Result Case from an attached .xdb file results in deleting all associated data with that attached .xdb file. i.e. deleting one Result Case deletes all Result Cases.

op2: Entry: PARAM,POST,-1
Results are read in as data blocks permanently into Patran
1) op2 file is a universal Nastran result file which can be imported/ read into different post-processors.
2) Time to read the op2 results into the Patran database is longer (data blocks are required to be read in).
3) Since the .op2 data is permanently attached to the Patran database, the overall size of the database increases considerably.
4) Though multiple op2 files can be attached to a single Patran database, the overall database size increases proportionally and it is confusing to identify the subcases that belong to a particular op2 file.
5) op2 file size is limited only up to 2GB.
6) op2 files has the flexibility by which it can be accessed from network drives or remote machine.
7) Individual Result Cases can be deleted in an op2 file attachment.