Header Pages

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Displays header page information in the database summary. Below is an example of database summary header page information, followed by an explanation of each item.

This function corresponds to the -header option of gstat.

Database "C:\Embarcadero\InterBase\examples\Database\employee.ib"

Database header page information:
Flags 0
Checksum 12345
Generation 41
Page size 4096
ODS version 12.0
Oldest transaction 29
Oldest active 30
Oldest snapshot 30
Next transaction 34
Bumped transaction 1
Sequence number 0
Next attachment ID 0
Implementation ID 16
Shadow count 0
Page buffers 0
Next header page 0
Database dialect 1
Creation date Aug 26, 2006 17:05:03

Variable header data:
Sweep interval: 20000
*END*

Service ended at 9/3/2006 4:59:05 PM

The first line displays the name and location of the primary database file while the remaining lines contain information on the database header page. These items include:

Header Page Information

Item	Description
Checksum	InterBase supports true checksums only for ODS 8 and earlier. For ODS 9 and later, the checksum value is always “12345”.
Generation	Counter incremented each time header page is written.
Page size	The current database page size, in bytes.
ODS version	The version of the database’s on-disk structure.
Oldest transaction	The transaction ID number of the oldest “interesting” transaction (those that are active, in limbo, or rolled back, but not committed).
Oldest active	The transaction ID number of the oldest active transaction.
Next transaction	The transaction ID number that InterBase assigns to the next transaction. The difference between the oldest transaction and the next transaction determines when database sweeping occurs. For example, if the difference is greater than this difference (set to 20,000 by default), then InterBase initiates a database sweep. See Overview of Sweeping.
Sequence number	The sequence number of the header page (zero is used for the first page, one for second page, and so on).
Next connection ID	ID number of the next database connection.
Implementation ID	The architecture of the system on which the database was created. These ID definitions are platform-dependent #define directives for a macro class named CLASS: 1 HP Apollo Domain OS 2 Sun Solaris SPARC, HP9000 s300, Xenix, Motorola IMP UNIX, UnixWare, NCR UNIX, NeXT, Data General DG-UX Intel 3 Sun Solaris x86 4 VMS 5 VAX Ultrix 6 MIPS Ultrix 7 HP9000 s700/s800 8 Novell NetWare 9 Apple Macintosh 680x0 10 IBM AIX POWER series, IBM AIX PowerPC 11 Data General DG-UX 88K 12 HP MPE/xl 13 SGI IRIX 14 Cray 15 SF/1 16 Microsoft Windows 7 (32-bit and 64-bit) 17 OS/2 18 Windows 16 bit 19 LINUX on Intel series 20 LINUX on Sparc systems 21 DARWIN on Intel 22 DARWIN on PowerPC 23 DARWIN on iOS ARM architecture 24 Android on x86 architecture (emulator) 25 Android on ARM architecture (device
Shadow count	The number of shadow files defined for the database.
Number of cache buffers	The number of page buffers in the database cache.
Next header page	The ID of the next header page.
Database dialect	The SQL dialect of the database
Creation date	The date when the database was created.
Attributes	force write—indicates that forced database writes are enabled. no_reserve—indicates that space is not reserved on each page for old generations of data. This enables data to be packed more closely on each page and therefore makes the database occupy less disk space. shutdown—indicates database is shut down.
Variable header data	sweep interval secondary file information