---
name: "pmaTryDeltaInDom"
section: "3"
platform: "linux"
package: "pcp"
version: "7.2.2-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/pmaTryDeltaInDom"
---

# pmaTryDeltaInDom(3)

try to translate a physical indom record from a \`\`full indom'' to a \`\`delta indom''

## NAME

**pmaTryDeltaInDom** - try to translate a physical indom record from a \`\`full indom'' to a \`\`delta indom''

## C SYNOPSIS

**#include \<pcp/pmapi.h\>**\
 **#include \<pcp/libpcp.h\>**\
 **#include \<pcp/archive.h\>**

**int pmaTryDeltaInDom(\_\_pmLogCtl \****lcp***,** **\_\_int32\_t \*\****rbuf***,** **\_\_pmLogInDom \****lidp*);

cc ... -lpcp\_archive -lpcp

## CAVEAT

This documentation is intended for internal Performance Co-Pilot (PCP) developer use.

These interfaces are not part of the PCP APIs that are guaranteed to remain fixed across releases, and they may not work, or may provide different semantics at some point in the future.

## DESCRIPTION

The input instance domain is passed in as either a physical metadata record via *rbuf* or in the \`\`loaded'' format identified by *lidp*. As these are alternate formats for the input instance domain, **pmaTryDeltaInDom** demands that **exactly** one of *rbuf* and *lidp* must be **NULL**, else the return value is -2.

The input instance domain is on the path to being written to the archive identified by *lcp*.

If possible, the instance domain will be converted to the \`\`delta indom'' format, and the converted instance domain returned via *rbuf* or *lidp* (whichever is not **NULL**). If conversion takes place, any storage associated with the input instance domain will have been free'd.

The \`\`delta indom'' format is only supported for Version 3 archives and it is the caller's responsibility to determine if calling **pmaTryDeltaInDom** is appropriate.

To determine if the \`\`delta indom'' format is the most efficient encoding, **pmaTryDeltaInDom** maintains a per-instance domain cache of the last seen \`\`full'' instance domain. To avoid data corruption, this means **pmaTryDeltaInDom** first copies the input instance domain. The copy and the cache are all managed privately by **pmaTryDeltaInDom** so the caller is unaware of this activity.

The caching scheme requires that the caller must call **pmaTryDeltaInDom** for **every** instance domain record, independent of whether the \`\`delta indom'' format is likely to be appropriate.

## DIAGNOSTICS AND RETURN VALUES

In several places, fatal errors will trigger an error message and force the application to exit.

A return value of -1 indicates that *rbuf* was not **NULL** and the physical record therein was not a **TYPE\_INDOM** (Version 3 \`\`full'' instance domain) record as expected. A return value of 1 means *rbuf* or *lidp* has been rewritten, and is now a **TYPE\_INDOM\_DELTA** record. Otherwise the return value is 0.

## SEE ALSO

[**pmaDeltaInDom**(3)](/pmaDeltaInDom/3.md), [**PMAPI**(3)](/PMAPI/3.md) and [**pmaUndeltaInDom**(3)](/pmaUndeltaInDom/3.md).